Tray-Shaped Article Having Smooth Edges and Amenable to Multiple Film Sealing Methods

ABSTRACT

The disclosure relates to forming shaped thermoplastic articles having smooth peripheries. Many thermoplastic articles have sharp edges formed upon molding or cutting the article from a feedstock sheet. Such sharp edges can damage thin plastic films or flesh which they contact, and smoothing the edges is desirable. Described herein are methods of forming a smooth periphery for such sharp-edged articles by rolling over the sharp edge. The smoothing operation is performed by forming a deflectable flange including a bend region separated from the potentially sharp peripheral edge by a spacer, deflecting a portion of the deflectable flange, and softening at least one bent portion of the deflectable flange to yield a smooth periphery upon cooling.

CROSS-REFERENCES TO RELATED APPLICATIONS

This application is a continuation-in-part of co-pending U.S.non-provisional patent application Ser. No. 15/445,220, filed 28 Feb.2017, which is a continuation-in-part of co-pending internationalapplication PCT/US16/49692, filed 31 Aug. 2016, which is entitled topriority to U.S. provisional patent application No. 62/212,367, filed 31Aug. 2015, each of which applications is incorporated herein byreference in its entirety.

BACKGROUND OF THE DISCLOSURE

This disclosure relates generally to the field of forming shapedthermoplastic articles.

Formation of shaped articles from thermoplastic materials is well known.A wide variety of methods (e.g., thermoforming, casting, molding, andspinning) can be used to confer shape to a molten thermoplastic or to apreformed thermoplastic sheet that has been softened or melted.

Trimming of waste material from one or more edges of a shaped article isa common finishing technique, but leaves a sharp edge that can injureflesh or tear or cut materials which come into contact with the edge.One common use for shaped thermoplastics is to form containers that canbe sealed with thin plastic films, such as trays, bowls, or binsintended to contain foodstuffs and intended to be sealed withtransparent plastic film. Another common use is to contain items and toseal them from moisture or other materials which may come into contactwith the container. Sealing of such containers typically involvesextending or stretching the film across a compartment formed in thecontainer and sealing the film around the periphery of the compartment,which periphery is often situated adjacent a trimmed edge of the articlethat includes the compartment. If that edge is sharp, it can cut orbreak the film, interfering with the sealing process.

Three well-known sealing technologies are commonly used in sealing foodsand foodstuffs to form containers for commercial shipping, storage,display, and sale. These are referred to herein as OW, VSP, and MAPtechnologies. All of these technologies involve combining a containerand a thin plastic film. Owing to the fragility of such films and theneed, in many instances, to minimize or eliminate punctures and tearsfrom film portions which serve to define (together with the container)sealed compartments, it is critical to minimize the opportunities forcontainers to tear, puncture, or abrade the film of the same or nearbycontainers. In addition to plastic films used for sealing suchcontainers, plastic films are also employed for shipping the containers,such as the “mother bags” (i.e., typically thin plastic bags) used forcontaining multiple product-in-container-packages during shipping andthe plastic grocery bags used by consumers to transport purchased goodsfrom a retailer. This can be achieved by reducing or eliminating sharpor rough container edges, at least positions on the container at whichsuch edges might reasonably contact the film during packaging, storage,shipment, or display.

Overwrap (OW) technology involves enveloping or wrapping a shapedarticle (e.g., a thermoformed tray, sheet, bowl, or multi-compartmentcontainer) with a thin (often transparent) plastic film after afoodstuff or other item has been placed on one or more faces of thearticle and thereafter sealing the film to itself (e.g., by heatingoverlapping portions of the film). In such OW technology, sharp or roughedges of the shaped article can cut, abrade, or puncture the film,potentially allowing materials to pass through the film and defeatingone or more of its purposes. Heretofore, OW technology has been usedprimarily together with foamed trays or bins lacking sharp edges. Manymunicipal recycling schemes exclude or disfavor foamed plastics, andsuch materials are therefore increasingly disfavored by consumers. Itwould be desirable if a thermoformable plastic container suitable foruse with multiple wrapping technologies, including OW technology, couldbe made, since thermoformable materials tend to be widely acceptable inrecycling programs.

Vacuum-sealed package (VSP) technology involves adhering a thin (again,often transparent) plastic film against a face of a shaped articlebearing a foodstuff (for example, or a moisture-sensitive object as analternate example) on a face of the shaped article. When VSP technologyis employed, that item(s) to be packaged are placed on a surface orwithin a cavity of the shaped article, the film is overlain such thatthe item(s) are interposed between the shaped article and the film, air(or whatever other gases may be present) is withdrawn from the spacebetween the film and the shaped article (optionally in coordination ofapplication of positive pressure to the exterior of one or both of thefilm and the shaped article) so that the film is closely opposed againstthe surface of the shaped article and/or the item(s), and the film issealed (e.g., by way of an interposed adhesive, through heat-inducedadhesion, or by static charge adhesion) to the surface of the shapedarticle across the desired area (usually completely encircling theitem(s)), and any excess film can be trimmed from the desired area. Theseal can be resistant to gas flow in order to maintain the gas-evacuatedstate on the interior of the sealed container. The resulting VSP-sealedpackage typically has a topology that mimics the shape of the surface ofthe shaped article having the item(s) thereon.

MAP is an abbreviation for modified atmosphere packaging and refers to asealing technology in which a flexible (often transparent) film issealed (e.g., using heat or an adhesive) about the perimeter of asubstantially rigid shaped article. When the shaped article is otherwiseclosed (i.e., when it has no other openings than that sealed by thefilm), the gases present within the container can be controlled at thetime the film is sealed to the article. Thus, if the article and filmare sealed in the presence of a selected atmosphere (e.g., a gas, suchas one selected to exclude oxygen or to promote fruit ripening), theselected atmosphere can be maintained within the sealed MAP packageduring subsequent storage, shipping, and display of the package.

As is known in the art, the shaped articles used in OW, VSP, and MAPsealing processes tend to have a variety of industry-accepted geometricshapes and properties which differ among the three types, such that ashaped article useful in one type of sealing process is often poorlysuited for use in one or both of the others.

Containers used for OW-sealing, for example, tend to be rectangular andtray- or sheet-shaped, with smooth, blunt edges and rounded corners. Thelack of sharp, rough, or pointed edges or corners serves to reduce thelikelihood that the film used for overwrapping the container will betorn or punctured upon wrapping. OW-containers often have a flat portion(e.g., on the “bottom” of the container, relative to its intendeddisplay configuration) at which the overwrapped film can be urgedagainst itself for the purpose of sealing the film to itself (e.g., uponapplication of heat to the overlapping film portions sufficient to causesuch sealing), thus enclosing the container and any items on or in it.

Containers used for VSP-sealing tend to have a face or surface(sometimes within a concavity) adapted to carry an item to be sealedbetween the film and the container and adapted to receive the sealingfilm by virtue of the absence of sharp points, protrusions, or edges.The absence of such features reduces the likelihood of punctures ortears in the film as it is drawn against the surface. UnlikeOW-containers, VSP-containers can have sharp edges, corners, orprotrusions, at least at portions other than the film-receiving surface,because those portions need not contact the film during sealing.However, such sharp portions can still damage sealing films, especiallywhen multiple VSP-sealed packages are stored, shipped, or displayed nearone another, because a sharp portion of one container can damage thefilm of another container (or a film or tissue in the vicinity of thecontainer).

Containers used for MAP-sealing tend to have a planar surface (e.g., abroad, flat rim) surrounding an opening to be sealed by applying a sheetof film against it, sealing the film to the surface (often substantiallyirreversibly), and then trimming the film about the perimeter of theseal. Such containers must be configured such that the film can beapplied to the surface without substantial risk of tears or puncturesbefore and during sealing and to facilitate trimming of the film fromthe sealed container. However, because the film typically contacts onlylimited portions of MAP-containers during the sealing process,MAP-containers can, and often do, include sharp, pointed, or abrasivefeatures at positions not involved in the sealing process.

It would be beneficial if the sharp edges of shaped thermoplasticarticles could be displaced in such a way that the risk of injury ordamage to sealing films could be reduced. It would be further beneficialif such individual shaped articles could be used with multiple knownsealing technologies, such as two or more of OW, VSP, and MAPtechnologies.

Reducing the sharpness and tendency of thermoformed articles to inducedamage and injuries would be advantageous even in the absence ofsealing. The subject matter disclosed herein addresses this shortcomingof prior shaped thermoplastic articles.

Others have recognized the desirability of reducing the occurrence ofsharp edges at the edges of trays to be overwrapped. For example, Nelsonet al. (U.S. patent application publication number 2015/0001127)disclosed a packaging tray that is formed by thermoforming a film sheetto yield a precursor tray having a generally U-shaped flange about itsperiphery, the open end of the U facing the sealing surface and theperipheral edge of the tray jutting peripherally. Nelson's tray is madeby cutting the precursor tray from a sheet of thermoformable material toyield an end in which the peripherally-extending peripheral edge ispositioned at the terminus of the outer (relative to the tray body) armof the U. Nelson then compresses that outer arm inwardly toward the traybody, leaving a smoother crimped portion of the U-shaped flange at theperiphery of the tray, with the still-potentially-sharp peripheral edgeextending toward the sealing surface. In this way, Nelson et al.,generates a tray said to be suitable for overwrapping, an overwrappingfilm being intended to urge the outer arm of the U-shaped flange towardor against the inner arm. However, because the tray retains a sharpperipheral edge in a position in which it can cut films (the peripheraledge of Nelson's trays can be seen to contact both the film overwrap andthe film overwrapping an adjacent tray in Nelson's FIG. 13A, forexample), Nelson's tray remains unsuitable for all OW applications andgenerally unsuitable for use with VSP and MAP technologies. It would bepreferable that a tray used for VSP and/or MAP packaging lacks both asharp peripheral edge of the material from which the tray is formed(see, e.g., peripheral edge 120 in Nelson's FIG. 12A) and any relativelysharp crimp (see item 124 in Nelson's FIG. 12A), because such edges andcrimps are capable of snagging, puncturing, or tearing films, eitherduring or after the sealing process.

The subject matter disclosed herein includes shaped thermoformedarticles which are suitable for sealing with multiple technologies.

Thermoformed drinking cups having smooth, rolled edges are also known.Such cups are made by thermoforming cups having a flange about theperimeter of the cup opening, the flange including a potentially sharpperipheral edge at the flange end distal to the interior of the cup. Theflanged cups are stacked in a nested fashion, heated at their flangeportions, and then passed through helical rim-rolling threads to createthe rolled edge. Such technology is useful only for rolling the edgesurrounding a circular orifice, and is therefore of no practical use inmaking shaped articles having rolled edges surrounding non-circularopenings. Rolled-edge drinking cups are also not designed to facilitatewrapping or sealing with thin plastic films.

BRIEF SUMMARY OF THE DISCLOSURE

The disclosure relates to methods of displacing a sharp edge away fromthe periphery of an article made from a thermoplastic material, wherethe sharp edge might otherwise damage surfaces that contact theperiphery of the article. The disclosure also relates to articlesprocessed according to those methods and to equipment for performingsuch processing.

The disclosure relates to a method of forming a smooth edge (i.e., asmooth periphery) on an article made of a thermoplastic material. Themethod includes a step of forming a deflectable flange at an edge of thebody of the article. The deflectable flange includes a peripheral edgeof the thermoplastic material at the peripheral end of the deflectableflange, optionally on a peripheral flange that extends peripherally fromthe deflectable flange. In one embodiment, the peripheral flange isconnected by an elbow to a spacer and extends peripherally beyond thespacer by a peripheral flange distance. The peripheral flange distancecan be selected to yield a desired degree of deflection when it isimpinged against a surface. In one embodiment, the peripheral flangedistance is selected to be zero (i.e., the peripheral edge exists wherethe elbow would otherwise be. The spacer is connected by a bend regionto the body, the bend region defining an angle (which can be acute orobtuse, and is preferably approximately a right angle) between thespacer and the body. The deflectable flange is urged within the interiorof a cavity defined by an upper body, for example, the distance betweenthe elbow and the interior being smaller than the peripheral flangedistance, so that the deflectable flange is deflected at the bend regionupon impingement of a portion of the interior of the cavity on theperipheral flange. Sufficient heat is applied to the bent portion (here,the bend region) of the deflectable flange to soften the thermoplasticmaterial at the bend region. The upper body and the article areseparated, whereby the bend region remains deflected upon cooling,yielding a smooth edge (i.e., periphery) on the article.

This method can be used to form a smooth edge about the entire peripheryof the article. To do so, the deflectable flange is formed about alledges of the article and the interior of the cavity is configured tosimultaneously impinge upon the deflectable flange about all edges ofthe article when the deflectable flange is urged within the interior. Inthe resulting article, the peripheral edge is effectively ‘hidden’(e.g., it is behind the deflected peripheral flange or deflected awayfrom the periphery of the article) so that materials (e.g., thin plasticfilms or animal tissue) which contact the periphery of the article willbe less likely to contact the peripheral edge of the thermoplasticmaterial from which the article is made.

The disclosure also relates to a method of forming a sealed compartment.This method includes steps thermoforming a thermoplastic sheet to forman article having a concave compartment surrounded by substantiallyplanar sealing surface, cutting the article from the sheet peripherallyto the sealing surface, forming a smooth edge about the entire peripheryof the article as described herein, and thereafter sealing a top sheetto the sealing surface to form the sealed compartment. In one embodimentof this method, the top sheet is trimmed peripherally about the sealingsurface after it is sealed to the sealing surface. In anotherembodiment, the top sheet is heat-sealed to the sealing surface.

The disclosure further relates to a method of forming a sealedcompartment. This method includes steps of thermoforming a thermoplasticsheet to form an article having a concave compartment surrounded bysubstantially planar sealing surface, cutting the article from the sheetperipherally to the sealing surface, forming a smooth edge about theentire periphery of the article as described above, and thereafterwrapping and sealing a flexible plastic film about the article to formthe sealed compartment.

In some embodiments of the methods described herein, after urging thedeflectable flange within the interior of the cavity and beforeseparating the upper body and the article, a ram can be urged into theinterior, closely opposed against the interior, behind the deflectableflange to an extent that a face of the ram impinges upon and furtherdeflects the deflectable flange, for example, at the bend region. Theface can be substantially planar, for example. The face can also besubstantially perpendicular to the portion of the interior that impingesupon the peripheral flange. The face can define an obtuse angle with theportion of the interior that impinges upon the peripheral flange. Theface can have a concave profile, relative to the interior. If the ram isheated, urging the ram against the deflectable flange can cause bendingof the portions of the deflectable flange which contact the ram, furtherdeflecting the peripheral edge of the thermoplastic sheet away from theperiphery of the shaped article.

In a non-heat-based embodiment, the disclosure relates to a method offorming a smooth edge on an article made of a plastic material (e.g., athin plastic material backed by a deformable metal layer). This methodincludes forming a deflectable flange at an edge of the body, thedeflectable flange including a peripheral edge of the thermoplasticmaterial at the peripheral end of a peripheral flange. In oneembodiment, the peripheral flange is connected by an elbow to a spacerand extends peripherally beyond the spacer by a peripheral flangedistance (which is effectively zero if there is no peripheral flange).The spacer is connected by the bend region to the body or an extensiontherefrom. The bend region defines an angle (which can be acute orobtuse, and is preferably approximately a right or slightly obtuseangle) between the spacer and the body. The deflectable flange can urgedwithin the interior of a cavity defined by an upper body, the distancebetween the spacer and the interior being smaller than the peripheralflange distance or impinged upon a shaped ram surface that deflects thedeflectable flange inwardly. The deflectable flange is therebydeflected, such as at the bend region, upon impingement. Sufficientpressure is applied to irreversibly bend the plastic material. The upperbody and the article are separated, whereby the deflectable flangeremains deflected upon removal of pressure, yielding a smooth edge onthe article.

BRIEF SUMMARY OF THE SEVERAL VIEWS OF THE DRAWINGS

FIG. 1 consists of FIGS. 1A, 1B, and 1C and illustrates the basicoperation of the structures and methods described herein. Parallelstraight lines “II” indicate positions at which structures, dimensions,and proportions which can optionally be present are omitted for clarity.

FIG. 1A illustrates a sectional view of a thermoplastic article 100having a deflectable flange 160 formed at an edge thereof. Thedeflectable flange 160 in this embodiment includes an extension 50, abend region 150, a spacer 140, and a peripheral flange 120. Theextension 50 connects the shaped body 10 of the article 100 to the bendregion 150 of the deflectable flange 160. A spacer 140 can be (andpreferably is) interposed between the bend region 150 and the peripheralflange 120. The peripheral flange 120 is connected to the spacer 140 byway of an elbow 130, which is shown as a right-angle bend in thisembodiment. The bend region 150 connects the extension 50 and the spacer140 at an approximately right angle (the angle designated A). Theperipheral flange 120 terminates at the peripheral edge 110 of thethermoplastic material (represented by a thick solid line in thisfigure) of which the article 100 is formed.

FIG. 1B illustrates the thermoplastic article 100 inserted within theinterior of an upper body 200, which is shown as a broken-away portion(indicated by the rough line). In this embodiment, impingement of theperipheral edge 110 of peripheral flange 120 upon the inner surface 202of the upper body 200 causes the deflectable flange 160 to defect, owingto bending of the deflectable flange 160 at one or more points B withinthe bend region 150.

FIG. 1C illustrates the outcome of inserting ram 300 (only a broken-awayportion shown, as indicated by the rough line) into the interior of theupper body 200 behind the thermoplastic article 100 (i.e., when the ram300 is inserted into the structures illustrated in FIG. 1B). The ram 300is closely opposed against the inner surface 202 of the upper body 200and the the peripheral edge 110 of peripheral flange 120 impinges uponthe upper face 302 of the ram 300, causing even greater deflection ofthe deflectable flange 160 and yielding a rounded periphery to article100 at the point(s) B at which bending is induced within the bend region150.

FIG. 2 consists of FIGS. 2A, 2B, 2C, and 2D and illustrates a matchedupper body 200 and ram 300 for deflecting one or more deflectableflanges 160 formed on the periphery of a shaped thermoplastic articlehaving the conformation of a rectangular tray with rounded corners. FIG.2A illustrates the upper body 200 disposed above the ram 300, and FIG.2B illustrates the upper body 200 engaged with the ram 300. FIG. 2C is acutaway view of the engaged upper body 200 and ram 300 shown in FIG. 2Band illustrates that a portion of the ram 300 fits within and closelyopposed to the interior surface of a recess in the upper body 200. FIG.2D is a detail of the section indicated in FIG. 2C and illustrates theclose opposition between the ram 300 and the interior of the upper body200. In FIG. 2D, the sloping conformation of the upper face 302 of theram 300 is apparent.

FIG. 3 consists of FIGS. 3A, 3B, and 3C, which are images of a smoothedperiphery and corner of a clear, shaped thermoplastic article having theconformation of a rectangular tray with rounded corners. The article wassmoothed using an upper body 200 and ram 300 similar to thoseillustrated in FIG. 2. In FIG. 3A, a finger is visible within theinterior of the tray, and the smoothed corner is visible to the left ofthe finger. Also visible at the portion where the finger is located is astacking lug, which is a portion of the corner of the tray which extendsperipherally to a greater extent than the portion of the corner belowthe finger. Extending (downwardly in the figure) from the smoothedcorner is a smoothed straight sidewall of the tray. Wrinkling of theperipheral flange is visible beneath the smoothed corner, and deflectionof the peripheral flange under the smoothed straight edge can be seenbehind the corner on the left side of the figure. FIG. 3B is anotherview of a smoothed corner of a similarly-made tray, also seen from belowthe rim of the tray. The prominent extension at the corner just belowthe rim is a stacking lug. FIG. 3C is a view of the smoothed corner,with a finger pointing to a smooth region formed by bending, softening,bending, and cooling of the bend region of the deflectable flange. Thissmooth region can, for example, be urged against a thin plastic filmwithout tearing it easily, since the relatively sharp edge of thethermoplastic material from which the tray is formed is bent under thecorner, as shown in FIGS. 3A and 3B.

FIG. 4 illustrates a section taken through a storage container article100 being formed using the methods described herein (parallel straightlines “II” indicate positions at which structures, dimensions, andproportions which can optionally be present are omitted for clarity). Inthe figure, the article 100 has a deflectable flange 160 formed on eachof the sides of the container visible in the figure. A single upper body200 extends across the entire container, including around the sides atwhich the deflectable flanges 160 are located. A single ram 300 (onlytwo portions shown in the figure) has been inserted within the interiorof the cavity in the upper body 200 behind the article 100. Theperipheral edge 110 of the thermoplastic sheet from which article 100 isformed, infringes upon the upper face 302 of the ram 300 at eachdeflectable flange 160, causing the deflectable flange 160 to deflectinwardly toward the body of the article 100 by flexing at one or moreportions B of the bend region 150 of each deflectable flange 160.Application of heat at B in an amount sufficient to soften thethermoplastic sheet causes the deflectable flanges 160 to retainapproximately the conformation shown in this figure, with the peripheraledges 110 of the thermoplastic sheet positioned anti-peripherally (i.e.,within the periphery of the article 100, which occurs at the positionsindicated by B in this figure), yielding smooth peripheries to theformed container upon cooling of the softened portions.

FIG. 5 consists of FIGS. 5A, 5B, and 5C, each of which illustrates asection taken through a storage container article 100 being formed usingthe methods described herein (parallel straight lines “//” indicatepositions at which structures, dimensions, and proportions which canoptionally be present are omitted for clarity). In the figure, thearticle 100 has a deflectable flange 160 formed on each of the sides ofthe container visible in the figure. The deflectable flanges 160 havebeen deflected inwardly by infringement thereupon by the upper face 302of a single ram 300 (only two portions shown in the figure) at eachdeflectable flange 160. The peripheral edge 110 of the thermoplasticsheet from which article 100 is formed, infringes upon the upper face302 of the ram 300 at each deflectable flange 160, causing thedeflectable flange 160 to deflect inwardly toward the body of thearticle 100 by flexing at one or more portions B of the bend region 150of each deflectable flange 160. Application of heat at B in an amountsufficient to soften the thermoplastic sheet causes the deflectableflanges 160 to retain approximately the conformation shown in thisfigure, with the peripheral edges 110 of the thermoplastic sheetpositioned anti-peripherally (i.e., within the periphery of the article100, which occurs at the positions indicated by B in this figure),yielding smooth peripheries to the formed container upon cooling of thesoftened portions. In this embodiment, the two parts of the ram 300 areshown with different profiles (one flat and one curved), to illustratedifferences in deflection that can be induced by the different profiles.FIGS. 5A, 5B, and 5C differ in the distance between the elbow and theperipheral edge, this distance being greater in FIG. 5A than in FIG. 5Band being zero in FIG. 5C.

FIGS. 6A, 6B, 6C, 6D, and 6E illustrate deflectable flanges formed intray-shaped articles thermoformed from a sheet of thermoplasticmaterial. In each of FIGS. 6A and 6B, a finger touches the sharp edge(i.e., the peripheral edge 110 at the periphery of peripheral flange120) where the tray has been cut from the sheet. In these figures, thedeflectable flange has not yet been softened, deflected, and cooled, sothe sharp edge remains positioned about the periphery of the tray. Bycomparison, the sharp edge has been deflected inwardly and away from theperiphery of the trays shown in FIG. 3 and in the tray shown in thelower portion of FIG. 6C. The tray shown in the upper portion of FIG. 6Cis the same as that shown in the lower portion, differing in that thetray in the upper portion has not had its deflectable flange “rolledover” as the tray in the lower portion has. FIG. 6D is a view from theunderside of a rounded rectangular tray which has a “rolled over” edgeabout its entire periphery. The absence of sharp edges at or near theperiphery of this tray is visible. FIG. 6E is an oblique view of threeinitially-identical trays, each having a “rolled over” edge as describedherein, the degree to which the edge has been “rolled over” differingamong the three. The tray labeled “1” has a peripheral edge that hasonly barely been “rolled over” (i.e., the portion of the deflectableflange including the peripheral edge 110 has been deflected not morethan about 45 degrees inwardly from the plane of the remainder of thespacer 140, most which remains substantially flat in this tray. The traylabeled “2” has a peripheral edge that has been more fully “rolledover”—so much so that the peripheral edge 110 can nearly not be seen (ithas been ‘tucked’ behind the remaining visible portion of the spacer140). On the tray labeled “3,” the deflectable flange has been rolledover further still and the peripheral edge 110 cannot be seen. That thedeflectable flange of tray “3” has been rolled over to a greater degreethan that of tray “2” is detectable by virtue of the shorter portion ofspacer 140 that remains visible on tray “3” than on tray “2” (and thevisible portion of spacer 140 of each of trays “2” and “3” is shorterthan the visible portion of spacer 140 of tray “1.”) The three traysshown in FIG. 6E can thus be thought to illustrate discrete degrees of“rolling over” of the deflectable flange.

FIG. 7 consists of FIGS. 7A, 7B, and 7C and illustrate an embodiment inwhich an article 100 formed of a thermoplastic sheet (parallel straightlines “II” indicate positions at which structures, dimensions, andproportions which can optionally be present are omitted for clarity)resting on a horizontal surface (solid horizontal line) has itsperipheral edges smoothed as described herein. In this embodiment, anupper body 200 (two portions shown in this cross section) is loweredover the article 100 in the direction indicated by the open arrow,causing each of the article's two deflectable flanges 160 to deflectinwardly. In FIG. 7A, outwardly-flared portions of the upper body 200have just contacted the peripheral flanges 120 of the article 100 as theupper body 200 is lowered onto the article toward the horizontalsurface; the deflectable flanges are beginning to deflect at the areasmarked “B.” In FIG. 7B, the the upper body 200 has been lowered onto thehorizontal surface, and the peripheral edges 110 and the peripheralflanges 120 of the article 100 are partially deflected inwardly towardthe body 10 of the article 100. In FIG. 7C, the ram 300 has beeninserted, in the direction indicated by the open arrow, into a cavity inthe upper body 200 behind the article 100 and further deflects theperipheral flanges 120 (and, with them, the deflectable flanges 160)through bending of the thermoplastic sheet of which the article isformed at the areas marked “B.”

FIG. 8 consists of FIGS. 8A, 8B, 8C, 8D, 8Di, 8Dii, 8E, 8F, 8G, 8H, 8J,and 8K and illustrates deflection and rolling over of the deflectableflange 160, including the sharp peripheral edge 110 thereof using a ram300 as described herein. Each of FIGS. 8A-8C, 8E-8G, and 8H-8K is across-sectional view including only one edge of the article; the samedeflection and rolling over of the edge can be performed on multipleedges (e.g., all edges) of the article simply by using multiple rams ora ram that contacts all edges to be so treated.

FIGS. 8A, 8B, and 8C sequentially depict the effect of urging the shapedarticle 100 farther against the ram 300 in the direction indicated bythe open arrow in each figure, as can be seen by comparing the portionof the article appearing in the left portion of each figure. In theembodiment shown in FIGS. 8A-8C, the deflectable flange 160 lacks anelbow and a peripheral flange. The initial (pre-ram-impingement)conformation of the shaped article is that shown in FIG. 9A.

In FIG. 8A, the article has been urged against the ram such that itsdeflectable flange 160 contacts the upper face 302 of the ram at itsperipheral edge. The deflectable flange 160 deflects from itspre-contact position by virtue of resistance to movement encountered bythe deflectable flange as it contacts the inclined portion of the upperface 302. In the figure, the peripheral edge 110 of the deflectableflange rests against the upper face at a position where the inclinedportion of the upper face transitions to a curved contour and a portionof the spacer is in close proximity to the ram, which is heated andtransfers heat thereto.

FIG. 8B shows the effect of urging the article 100 depicted in FIG. 8Afurther against the ram 300. Because the ram 300 shown in FIG. 8B isheated, it softens the material from which the deflectable flange 160 ismade at portions where the deflectable flange is in close proximity toor contacts the upper face 302 of the heated ram 300. Because of theshape of the upper face 302, the deflectable flange 160 reaches aposition at which it can no longer advance by merely sliding along theupper face surface. Because the article 100 (including the deflectableflange 160) is being urged in the direction indicated by the open arrow,and because the material of which the deflectable flange is constructedhas been softened by the heated ram 300, the deflectable flange deforms(at positions B) to follow the contour of the upper face 302 of the ramas the deflectable flange is advanced against the ram.

FIG. 8C shows the effect of continuing to urge the article 100 depictedin FIG. 8B against the heated ram 300. As the article (including thedeflectable flange 160) is urged in the direction indicated by the openarrow, the deflectable flange continues to bend where softened bycontact with the heated ram (i.e., at positions B). As movement of thedeflectable flange against the ram continues, the peripheral edge 110 ofthe deflectable flange eventually reaches an edge of the upper face 302of the ram. The portion of the deflectable flange including theperipheral edge remains softened for a period of time (the period beingdependent on the operating conditions in predictable ways). If theperipheral end contacts a portion of the article 100 while softened, itcan be deflected thereby (e.g., upwardly, as suggested in the embodimentshown in FIG. 8C). Deflection of the portion of the peripheral flangeleaving contact with the upper face can also be influenced by thecontour of the upper face 302, for example inducing a “curled” or“spiraling” conformation as shown in FIG. 8C.

FIG. 8D illustrates using one or more objects to assist with deflectionand rolling over of the deflectable flange as describe herein. Object401 (referred to elsewhere herein as a plug) is disposed within aninterior compartment of the shaped article 100 and abuts against aninner surface of the shaped article 100 during impingement of thedeflectable flange 160 against the ram 300, in order to reduce orprevent inward deflection of the inner surface during the operation.Object 403 applies downward pressure (open arrow) against, in thisembodiment, the extension 50 portion of the deflectable flange 160, inorder to impinge the deflectable flange 160 against the upper surface302 of the ram 300. In this embodiment, object 402 rigidly connectsobjects 401 and 403. Filled arrows depict forces imposed upon thearticle 100 upon application of the downward pressure. FIG. 8Di depictsa shaped article in the form of a rounded rectangular tray T having aninterior and a plug P that is shaped and dimensioned to fit within thatinterior, so as to act as object 401 in FIG. 8D and to reduce or preventinward deflection of the side walls of the tray T during the rollingover of the deflectable flange of the tray T. FIG. 8Dii shows the pluginserted within the interior of the tray.

FIGS. 8E, 8F, and 8G (analogously to FIGS. 8A, 8B, and 8C) sequentiallydepict the effect of urging the shaped article 100 farther against theram 300 in the direction indicated by the open arrow in each figure. Inthe embodiment shown in FIGS. 8E-8G, the deflectable flange 160 includesa peripheral flange 120 at the peripheral end of the spacer 140. In thisfigure, it can be seen the peripheral flange 120 deflects during bendingof the deflectable flange 160 to the extent that it becomesindistinguishable from the spacer 140.

FIGS. 8H, 8J, and 8K (analogously to FIGS. 8A, 8B, and 8C; FIG. 8I isdeliberately omitted) sequentially depict the effect of urging theshaped article 100 farther against the ram 300 in the directionindicated by the open arrow in each figure. In the embodiment shown inFIGS. 8H-8K, the deflectable flange 160 includes a peripheral flange 120at the peripheral end of the spacer 140. In these figures, it can beseen the peripheral flange 120 deflects during bending of thedeflectable flange 160 to the extent that it becomes completely bentover the spacer 140, forming a ‘hook’-like structure. B in FIG. 8Jindicates that bending is occurring in the portion of the deflectableflange 160 spanning the indicated portion of the upper face 302 of theram 300.

FIG. 9 consists of FIGS. 9A, 9B, 9C, 9D, 9E, and 9F and illustrates abeneficial feature of one embodiment of the shaped articles disclosedherein.

FIG. 9A is a cross-sectional view of one edge of an article 100 showingthe conformation of its deflectable flange 160 prior to the rolling-overoperation described herein, including the property that the potentiallysharp or rough peripheral edge 110 is accessible to contact a film usedto seal the article or another nearby film or object. FIG. 9B is across-sectional view of one edge of an article 100 have a peripheraledge 110 rolled over by the technique illustrated in FIGS. 8A-8C.Relative to the article engaged with the ram illustrated in FIG. 8C, thedeflectable flange 160 of the article has ‘rebounded’ in a peripheraldirection following disengagement from the ram. Because the plasticmaterial of which the article is constructed is flexible, therolled-over edge shown in FIG. 9B exhibits ‘springiness’ when urged indirections normal to the plane of the figure, such as in the directionsindicated by the open arrows.

FIG. 9C is a cross sectional view of the edges of three of the articles100 shown in FIG. 9B, the articles being stacked in a nestedconfiguration. Because each of the article has the same shapes (e.g., atray like the one shown in the lower portion of FIG. 6C), each articlecan nest and be urged together until with others its rolled-over edgecontacts the tray above and/or below it. FIG. 9C illustrates threethus-stacked nested trays, with open arrows indicating positions atwhich standard de-nesting equipment can be employed to separate thenested trays. Fingers or threads, for example, can engage the inter-trayregions at these positions, the fingers or threads being operable (perordinary de-nesting procedures) to separate the trays from one anotherfor individual use.

FIG. 9D is an image of a prior art thermoformed plastic tray having astacking lug (the corner extension beneath the rim, toward which thefinger in the image is pointing). The stacking lug serves to maintain acontrolled separation distance between stacked trays, as shown in theleft portion of FIG. 9E (which is an image of two of these prior arttrays stacked against one another, with the inter-tray distance beinglimited by the stacking lug). The right portion of FIG. 9E shows twostacked, nested trays having rolled-over edges (as illustrateddiagrammatically in FIG. 9C with three trays). An inter-tray division isvisible between the rims of the two stacked trays. FIG. 9E illustratesthat two trays having rolled-over edges as described herein can bestacked in a separable way in a smaller volume than can prior art trayshaving stacking lugs. FIG. 9F shows, on its left side, three nested andstacked trays having rolled-over edges and having stacking extensions180 formed into the corners thereof to increase separation between thestraight edges of the stacked trays. The three stacked trays havingstacking extensions 180 can be seen to have greater separation (largebrackets on left side of figure) than the separation (small brackets onright side of figure) of three otherwise-identical stacked trays lackingstacking extensions.

FIG. 10 consists of FIGS. 10A, 10B, and 10C. FIG. 10A is an image of aram 300 having a shaped article 100 in the form of a rimmed, roundedrectangular tray borne thereby. In the lower right portion of the imagecan be seen the upper surface 302 in which a second article could bedisposed, but which does not currently bear an article. In the article100 borne by the ram 300 in the upper part of the figure, it can be seenthat the extension 50 connects the spacer 140 and peripheral flange 120portions of the deflectable flange to the body 10 of the article 100.The spacer 140 and peripheral flange 120 are carried by the uppersurface of the ram 300 in the upper part of the figure, and that uppersurface (analogous to upper surface 302 in the lower right portion ofthe figure) cannot therefore be seen directly. “10B” indicates a portionof the ram 300 shown (with the shaped article 100 removed) in FIG. 10B.In FIG. 10B, portions of the upper surface 302 of the ram 300 can beseen. Dashed line 10C-10C in FIG. 10B indicates the approximate positionof the cross-section depicted in FIG. 10C, and letters A-E are includedas landmarks so that the surface configuration of the ram 300 can bebetter understood by comparing FIGS. 10B and 10C. FIG. 10C is adiagrammatic cross-section of the ram 300 shown in FIG. 10B, includinglandmark letters A-E.

DETAILED DESCRIPTION

The subject matter disclosed herein relates to formation of shapedthermoplastic articles, and more specifically to articles which areformed such that one or more of the edges of the article has aconformation wherein the peripheral edge of a thermoplastic sheet fromwhich the article is formed is turned away from a face of the article,and preferably away from the periphery of the article, so that a fragilematerial (e.g., flesh or a thin, flexible plastic sheet) that is appliedagainst the face or periphery does not contact the edge of the sheet.Because such sheet edges can be sharp, especially when the edge has beencut or broken, directing the edge away from a face and/or periphery ofthe article can prevent damage to fragile materials which contact theface or periphery. The subject matter disclosed herein is of particularuse in forming containers which will be sealed with fragile plasticfilms applied against a face of the container or in which the containeris wrapped. In a preferred embodiment disclosed herein, the peripheraledge of the thermoplastic sheet from which the article is formed isturned away from the article's periphery so far that the resultingarticle is suitable for use in any or all of OW, VSP, and MAP sealingtechnologies. The shaped articles described herein are believed to bethe first packages which can, practically, be sealed using all three ofthese technologies. Desirably, thermoformable and moldable plastics tendto be widely acceptable in recycling programs, and articles madetherefrom can be more readily recycled than, for example, foamed plasticarticles.

Briefly summarized, the basic method described herein for forming ashaped thermoplastic article having a smooth edge involves forming adeflectable flange at the periphery of the article. The deflectableflange includes the potentially-sharp or -rough peripheral edge of thethermoplastic material from which the article is formed. The deflectableflange is softened (i.e., raised to a temperature at or above the glasstransition temperature of the material of which the flange is formed,and preferably a temperature less than the melting point of thematerial) at one or more portions thereof so that the peripheral edge isdirected away from the periphery of the article when the deflectableflange is deflected toward the body of the article (preferably ‘hiding’the peripheral edge between the deflected portion of the deflectableflange and the extension, the body, or both. Cooling (i.e., stiffening)the softened and deflected deflectable flange below its glass transitiontemperature “locks” the peripheral edge in that position, lessening thelikelihood that material (e.g. flesh or film) that contacts theperiphery of the article will be damaged by the sharpness or roughnessof the peripheral edge.

It is the presence of the deflectable flange formed at the peripherythat permits peripheral edges (and, particularly, curved edges andcorners of peripheral edges) to be “rolled over” to yield a smoothperiphery. In previous trays which included an exterior flange (e.g., atray having a periphery like that shown in FIG. 1A, lacking the bendregion 150, the spacer 140, the elbow 130, and the peripheral flange120, and having the peripheral edge 110 at the periphery of theextension 50), bending or rolling of the exterior flange might have beenpossible along straight edges, but bending or rolling curved edges andcorners of such exterior flanges could not be performed without bucklingor wrinkling of the material in the flange, yielding an undesirablenon-smooth edge. It is the presence of the smooth bend region 150 andthe spacer 140 of the deflectable flange described herein that permitsthe peripheral edge 110 to be deflected away from the periphery of thearticle without such buckling or wrinkling, yielding a smooth periphery.It can be seen from FIGS. 1, 4, 5, 7, and 8 that the bending, flexing,and curling that the deflectable flange undergoes can be effected in anyone or more of the extension 50, the bend region 150, the spacer 140,the elbow 130, the peripheral flange 120, and even at the peripheraledge 110. Whichever one or ones of these elements are caused to bend ordeflect in order to achieve the effect, the resulting disposition of thepotentially sharp peripheral edge 110 away from the periphery of thearticle, and preferably not reasonably accessible from the exterior ofthe article at its periphery yields an article having a smooth peripherywhich is suitable for contacting with fragile films, tissues, or othersurfaces.

In one embodiment, the deflectable flange includes a peripheral flangethat juts outs in a peripheral direction from the article and isattached to a spacer portion by way of an elbow (e.g., a 90-degree turnor a turn through some other offset angle, such as one of 60-120degrees) in the thermoplastic material that forms the article. The bodyof the article is attached to the spacer by way of a bend region, whichdefines an angle (angle A in FIG. 1A; preferably an approximately rightangle) between the spacer and the portion of the body adjacent the bendregion (i.e., this portion will usually be the extension which serves toconnect the body to the bend region). The deflectable flange is insertedinto the interior of a cavity in a body (e.g., an upper body 200 or aram 300) such that the peripheral flange is impinged by a wall ofcavity, thereby deflecting the deflectable flange in the direction ofthe body of the article. Upon such deflection, heat is applied to thebend region that is sufficient to soften or melt the thermoplasticmaterial at the bend region, so that the deflectable flange remainsdeflected toward the body when the bend region cools. Optionally, a ramcan be inserted into the cavity after the deflectable flange, and a faceof the ram which contacts the deflected peripheral flange can inducefurther deflection of the deflectable flange, further displacing theperipheral edge of the article away from the periphery of the articleupon cooling. In this way, a smooth, “rolled” edge of the thermoplasticmaterial forms the outermost periphery of the article, while theperipheral edge of the thermoplastic material remains within theoutermost periphery of the article, where the sharpness of that edge isless likely to damage fragile materials which contact the outermostperiphery of the article.

In another embodiment, the deflectable flange is contacted with a ramthat deflects the deflectable flange in a direction that deflects thesharp edge of the thermoplastic sheet away from the periphery of thearticle. Before, during, or after such deflection, one or more portionsof the deflectable flange (e.g., the bend region, the spacer, the elbow,the peripheral flange, any portion(s) that contact the ram, or acombination of these) are heated sufficiently to soften thethermoplastic material, and the deflectable flange is thereafter cooledto “lock in” the deflection. Depending on the degree of deflection, theperipheral edge of the thermoplastic material can be simply turned awayfrom the periphery of the article, turned in a direction approximatelyopposite the periphery, or even “rolled up” by deflecting thedeflectable flange at a sufficiently tight radius while it is softenedthat a J-shaped, U-shaped, or even spiral-shaped conformation isachieved (i.e., any shape yielding a substantially smooth peripheraledge), with the peripheral edge being thereby rendered virtuallyincapable of damaging flesh or film present at the periphery of thearticle.

Individual elements and aspects of the shaped articles and methods formaking them are now described in greater detail.

The Shaped Article

The methods described herein are believed to be applicable to articleshaving a wide range of shapes and sizes, especially articles whichnormally have a sharp peripheral edge when made by common methods.Motivation for making shaped thermoplastic articles with smooth edgesstemmed in part from a desire to make common storage trays (e.g.,plastic trays used for storing foodstuffs such as fresh or frozen meats,fruits, or vegetables) having edges that are sufficiently dull(non-sharp) that the trays can be wrapped in or contacted with thinplastic films such as polyvinylidene chloride and polyethylene filmswithout the film being cut or punctured by the tray edge under normalusage conditions. However, once the methods described herein weredeveloped, it was recognized that the smooth, rounded edges aredesirable in a variety of other situations, such as preventing injury tothe flesh of humans handling trays and other shaped articles andpreventing damage to films sealing one tray by sharp edges of a secondsealed tray (e.g., as in a shipping container containing multiple sealedtrays).

By way of example, a common method of making shaped articles such asmeat trays is by thermoforming a sheet of a thermoplastic. Inthermoforming processes, a portion of a long sheet of a thermoplastic israised to a temperature at which the thermoplastic softens and can bemolded. The softened thermoplastic is applied against the surface of oneor more molds (often with the aid of negative air pressure to ensure atight opposition of the softened thermoplastic film against the moldsurface). As the film cools (e.g., upon contact with the mold surface),the thermoplastic hardens and becomes less easily deformable, resultingin the thermoplastic film attaining and retaining the shape imposed uponit by the molding process. Multiple casts are often made of the samearticle in a single sheet of film in thermoforming processes, and theindividual articles are freed from the film by cutting (e.g., diecutting) the film about the periphery of the article. This process tendsto yield a sharp edge at the cut portions of the film, including a sharpedge that surrounds all or a portion of the periphery of the article(i.e., where the article was cut from the film).

Further by way of example, a thermoplastic material can be melted in anextruder and injected into a mold cavity which defines the shape of themolded article. After cooling, the mold can be opened to release themolded article. In molding processes, it is common for thermoplasticmaterial to appear at parts of the finished articles where it is notdesired, such as “flashing” that occurs when molten thermoplastic flowsbetween mold plates or at the ports through which the moltenthermoplastic was fed into the closed mold. These non-desired parts canbe sharp in their own right, and sharp edges can be left when thesenon-desired parts are cut from the molded article.

The size and shape of the articles described herein are not critical. Ingeneral, the shaped articles will be ones for which handling of thearticles or contact between peripheral edges of the article and one ormore fragile materials is anticipated. The edge-smoothing processdescribed herein can remove one or more sharp edges from thermoplasticarticles which normally have such sharp edges, regardless of themethod(s) by which the articles are produced.

The Smoothing Method

The periphery of a thermoplastic article—particularly one formed from abent or shaped sheet of a thermoplastic material—can be smoothed by aprocess that includes forming a deflectable flange near the periphery ofthe edge to be smoothed, deflecting a bent portion of the flange todisplace the edge from the periphery of the article, softening the bentportion at least while the flange is in the deflected position, andre-hardening the bent portion while the flange is in the deflectedposition. This process is illustrated in FIG. 1. The portion of thedeflectable flange 160 that can be softened and bent can be the bendregion 150 or, preferably, a portion of the deflectable flange distal tothe bend region 150, but proximal to the peripheral edge 110. By way ofexample, softening the spacer 140 permits its peripheral portion,including the elbow 130, peripheral flange 120 (if these two elementsare present), and peripheral edge 110 to be bent inwardly (i.e., towardthe body 10 of the article 100) sufficiently to displace the peripheraledge 110 away from the periphery of the article.

Preferably, at least a portion of the spacer 140 is softened and bentsufficiently that the peripheral edge 110 is “rolled over,” such thatthe peripheral edge 110 is positioned such that a film that overwrapsthe article or that is draped across the article does not contact theperipheral edge 110, even if pulled taut. Still more preferably, thedeflectable flange 160 is rolled over sufficiently that the peripheraledge 110 is visually obscured by the spacer 140 or the bend region 150such that the peripheral edge 110 cannot be seen when the article 100 isviewed horizontally from it periphery (i.e., from its peripheral side).Also preferably, the deflectable flange 160 is rolled over sufficientlythat the peripheral edge 110 “points” toward the body 10 or toward theunderside of a portion of the deflectable flange 160, meaning that theplane of the deflectable flange at the portion including its peripheraledge 110 intersects the body 10, including the underside 161 (see FIG.1B, for example) of the deflectable flange 160. When the plane of thedeflectable flange at its edge including the peripheral edge 110 doesnot point at the body 10 or the underside 161 of the deflectable flange160, then that peripheral edge should at least be displaced far enoughfrom the periphery of the article 100 or rolled over sufficiently toobscure the peripheral edge 110 by one or more portions of thedeflectable flange 160.

FIG. 1A illustrates a thermoplastic article 100 having a body 10 (with,in this figure, an irregular shape) and a deflectable flange connectedwith the body 10. The deflectable flange includes a peripheral flange120 which includes a peripheral edge 110 of the thermoplastic sheet fromwhich the article 100 is formed. The deflectable flange also includes abend region 150 interposed between the body 10 of the article 100 andthe peripheral flange 120. The bend region 150 is separated from thebody 10 by an extension 50, which is simply a flat portion of thethermoplastic sheet in this embodiment. The peripheral flange 120 issimilarly separated from the bend region by a flat portion of thethermoplastic sheet designated the spacer 140 in this embodiment. Theperipheral flange 120 is connected to the remainder of the deflectableflange by an elbow 130 which, in this embodiment, is a portion of thethermoplastic sheet formed into a right angle.

FIG. 1A is a cross-section of such an article 100, in which the solidblack line represents the cross-section of the thermoplastic sheet fromwhich it is formed. The peripheral edge 110 forms the periphery of thearticle 100 because no other portion of the article 100 extends fartherto the right (in this figure), the spacer 140 and the other portions ofthe peripheral flange 120 being nearer to the body 10 than theperipheral edge 110 of the sheet. Thus, if an object were urged againstthe right side (in FIG. 1A) of article 100, the object would tend tocontact peripheral edge 110 and the sharpness of that peripheral edge110 could affect the object, such as by cutting, damaging, or injuringthe object.

In FIG. 1B, the thermoplastic article 100 is inserted within an interiorcavity of an upper body 200. The inner surface 202 of the upper bodyimpinges upon the peripheral flange 120, deflecting it inwardly (i.e.,anti-peripherally) toward the body 10 of the article 100. In thisembodiment, both the peripheral edge 110 of the thermoplastic sheet fromwhich the article 100 is formed and the peripheral-most portion of thebend region 150 are positioned about equally peripherally from the body10. Preferably, the deflectable flange 160 is deflected inwardlysufficiently far that the peripheral edge 110 of the thermoplastic sheetis contained within the interior cavity of the upper body 200. In thisembodiment, the spacer 140 is essentially rigid and substantially allbending occurs within the bend region 150. If heat sufficient to softenthe thermoplastic sheet is applied to the bend region 150 (atapproximately the location identified as “B” in FIG. 1B) and the sheetis subsequently cooled (preferably below its glass transitiontemperature), then the deflectable flange 160 will retain theconfiguration shown in FIG. 1B (i.e., deflected relative to its initialconformation shown in FIG. 1A on account of impingement of theperipheral edge 110 against the inner surface 202 of the upper body 200)even after upper body 200 is separated from the article 100. In thisdeflected conformation, the peripheral edge 110 does not extendperipherally beyond the rounded bend region 150, and the resultingarticle will be more suitable for sealing with a thin plastic filmapplied to extension 50 and bend region 150 than was the original,pre-deformation article shown in FIG. 1A (i.e., on account of theprotuberance of potentially sharp peripheral edge 110 beyond theperiphery of bend region 150, at which position the peripheral edge 110might readily snag, abrade, or cut the film).

FIG. 1C illustrates an optional, but preferable step in which a ram 300is inserted within the cavity in the upper body 200 behind the article100 (i.e., sandwiching at least the deflectable flange 160 between theupper body 200 and the ram 300). This step further deflects (relative tothe embodiment show in FIG. 1B) the deflectable flange 160 towards thebody 10 of the article 100, thereby displacing the (potentially sharp)peripheral edge 110 of the thermoplastic sheet further from theperiphery of the article (i.e., farther from inner surface 202 of theupper body 200). Heating the bend region 150 of the deflectable flange160 sufficiently to at least soften it while it is in the conformationshown in FIG. 1C and subsequently cooling it below its glass transitiontemperature will ‘freeze’ the deflectable flange in the conformationshown. In this conformation, the sharp peripheral edge 110 of the sheetfrom which the article is formed is ‘tucked’ under other portions (e.g.,the bend region 150 and the extension 50, if present) of the deflectableflange 160, and is consequently less accessible to objects contactingthe periphery of the article (and less liable to tear, cut, or injurematerials which contact the periphery of the article). For example, if athin plastic film is applied to extension 50 and bend region 150, thenthe film is even less likely to be snagged, abraded, or cut by thepotentially sharp peripheral edge 110 in this embodiment than it was inthe embodiment shown in FIG. 1B. From this progression (i.e., greaterdeflection in FIG. 1C than in FIG. 1B and FIG. 1A), it can be seen thatthe more the peripheral edge 110 is deflected away from the periphery ofportions of the article to which a sealing film is applied, the lesslikely damage to the film from the edge becomes.

The ram 300 and the upper body 200 each serve the purpose of deflectingthe deflectable flange by impacting upon or against it. These two itemsare therefore essentially interchangeable and can each be used alone orin combinations two or more ram(s) and upper body(ies). In thisdisclosure, the term “ram” is used to refer to a body that impinges uponthe deflectable flange by being applied thereto or thereagainst in adirection from the portion of the deflectable flange most distal fromthe body of the shaped article. Similarly, the term “upper body” is usedto refer to a body that impinges upon the deflectable flange by beingapplied thereto or thereagainst in about the opposite direction (see,e.g., FIGS. 1C and 4).

In the example shown in FIG. 1C, the portions of the ram 300 whichimpinge upon the peripheral flange 120 of the deflectable flange 160while the article is lodged within the cavity in the upper body 200 hasa wedge-shaped cross section. Such a ram can be useful for directing theperipheral flange 120 and peripheral edge 110 anti-peripherally, in thatthe farther the ram is advanced within the interior in the directionfrom the peripheral edge 110 toward the bend region 150, the farther theperipheral flange 120 and peripheral edge 110 will be deflected in ananti-peripherally direction. However, these portions of the ram 300 neednot be wedge-shaped. Substantially any shape of ram 300 that willdeflect the peripheral flange 120 and peripheral edge 110anti-peripherally when the ram 300 is inserted behind the article 100 inthe upper body 200 can be used, such as blunt or rounded (convex orconcave at its upper face 302), or a combination of any of these, can beused, for example as shown in FIG. 5.

FIG. 8 illustrates an alternate method of rolling or otherwise shapingthe edge of an article. As can be seen in FIG. 8A, the deflectableflange 160 in this embodiment lacks an elbow or peripheral flange, andinstead includes only a spacer portion that terminates at the peripheraledge 110 of the thermoplastic sheet. This deflectable flange is urged(in the direction indicated by the open arrows in FIG. 8, regardless ofhow such urging is achieved, such as by moving either or both of thearticle 100 or the ram 300) against the upper surface 302 of a heatedram. When the direction of travel of the deflectable flange closelyparallels the conformation of the upper surface (i.e., as in FIG. 8A),relatively little of the deflectable flange may contact the uppersurface and relatively little heat may be transferred from the ram tothe deflectable flange. However, as shown in FIG. 8B, when relativemovement of the article and the ram cause greater surface contact orgreater proximity between the upper surface of the ram and thedeflectable flange, the interfacial area of contact/proximity can begreater, resulting in greater heat flow from the ram to the deflectableflange. Sufficient heat flow will result in softening of thethermoformable material, causing the deflectable flange to assume theconformation of the upper surface. When, as shown in FIG. 8C, stillfurther relative movement of the article and the ram is made, a greaterportion of the deflectable flange will be softened and deflected. Aswith the embodiment shown in FIG. 1B, it can be seen in this embodimentthat heat suitable for bending the deflectable flange is being applied(at multiple locations B in FIGS. 8B and 8C); however, in order to “rollover” the portion of the deflectable flange that includes the peripheraledge, little or no flexion, and no heat application, is occurring at thebend region 150 (other than perhaps to a small degree as theperipheral-most portions of the bend region 150 approach the heated ram300, as in FIG. 8C). For the purposes of the processes described herein,it is substantially immaterial which portions of the deflectable flangeare softened and bent, so long as the desired result is obtained: thepotentially sharp peripheral edge 110 is deflected away from theperiphery of the article and, preferably, sequestered (as in FIG. 8C)where it is very unlikely to contact any easily-damaged film or tissuewhich contacts the periphery of the shaped article. The deflectableflange can be contacted with, or brought into close proximity with, theram in a single smooth motion, in a plurality of discrete, incrementaladvances, or a combination of these, in order to permit portions of thedeflectable flange to soften sequentially.

As the thermoformable material moves out of contact with the ram (eitherby disengaging the two or, as shown in FIG. 8C as a portion of thedeflectable flange moves beyond the upper surface of the ram), thethermoformable material can cool and the deflection induced therein willbe retained upon cooling. As shown in FIGS. 9B and 9E, disengagement ofthe article and the ram results in a rolled-over edge of the article,the rolled-over edge having a smooth periphery and being suitable forhandling and/or contact with fragile plastic films. Although there is nodegree of deflection of the peripheral edge 110 that can unambiguouslybe identified as a “minimum” amount of deflection sufficient to preventcontact between that edge and fragile tissues or films in all possibleedge configurations, it can nonetheless be generally said that if thebent portion of the deflectable flange is bent sufficiently that theperipheral edge “points at” (i.e., a plane tangential to thethermoplastic sheet at and extending through the peripheral edgeintersects) any part of the deflectable flange (including, for examplethe extension, the bend portion, the spacer, or the bent portion) thenthis configuration should generally render the peripheral edgesequestered sufficiently to prevent that edge from contacting fragiletissues or films at or near the periphery of the article (see, e.g.,FIGS. 8C, 8G, and 9B). Alternatively, the deflectable flange can bedeflected sufficiently that peripheral edge 110 is closely opposedagainst a sidewall of the concave portion (see, e.g., FIGS. 8C, 8K and9B) or is nearer the extension 50 than is thefurthest-from-the-extension bent portion (as in FIGS. 8B, 8D, 8F, and8J) in order to achieve such sequestration. Preferably, the peripheraledge 110 is ‘contained within’ a compartment defined by the rolled overportion of the deflectable flange and either the sidewall of theconcavity (including, for example, as shown in FIG. 8K) or a portion ofthe deflectable flange completely around the periphery of the article,so as to render it substantially devoid of a sharp edge that can damagefragile tissues and plastic films in the vicinity of the article. Inanother embodiment, a flat-bottomed tray has a peripheral rim that isapproximately planar, the plane of the rim being essentially parallel tothe bottom (such as in standard MAP trays and other trays); for such aflat-bottomed tray, the rolled peripheral edge is preferably rolledsufficiently that it “points back at” the tray cavity (i.e., is parallelto the two planes, but oriented in the direction of the tray cavity) orfarther (e.g., is rolled over sufficiently that the peripheral edgepoints at the underside of the extension at the rim or to the undersideof the bent portion).

In FIG. 8A-8C, the deflectable flange was depicted lacking the elbow 130and peripheral flange 120 illustrated in FIG. 1A for the sake ofsimplicity of illustration. Although production of deflectable flangeslacking the elbow and peripheral flange is possible (e.g., bymechanically or laser-cutting the deflectable flange at the spacer 140shown in FIG. 1), such production can be difficult and costly and istherefore of limited practicality in large-scale production operations.For this reason, shaped articles 100, such as those intended for use aspackaging trays for food, that are processed described herein will oftenhave both the elbow and peripheral flange illustrated in FIG. 1A. Asillustrated in FIGS. 8E-8K, shaped articles bearing the elbow andperipheral flange can nonetheless be processed using the methods andequipment described herein.

FIGS. 8E-8G depict processing of a shaped article 100 that has adeflectable flange 160 that includes both the peripheral flange 120 andthe elbow 130 described herein, and the processing depicted in thesefigures is roughly analogous to that depicted in FIGS. 8A-8C. In FIG.8E, the peripheral edge of the deflectable flange 120 directly contactsthe upper surface 302 of the ram 300. Because the ram is heated, heat isconducted directly to the peripheral edge where it contacts the ram andby radiation from closely-opposed portions of the spacer 140. Bycontrolling heat flowing from the ram and the residence time of thearticle 100 in the position shown in FIG. 8E, an operator can inducesoftening of portions of the deflectable flange, particularly includingat its peripheral edge and at portions of the spacer near thatperipheral edge. Softening of these portions facilitates bending of thedeflectable flange at the softened portions, such as by urging thearticle further against the ram, such that a curved portion of the uppersurface will induce bending as the more-peripheral portions of thedeflectable flange are driven against the curved portion of the uppersurface by the less-peripheral portions (which transmit force applied tothe article), as shown in FIG. 8F. Further urging of the article againstthe ram, as shown in FIG. 8G, causes the portions of the deflectableflange that are in contact with the upper surface of the ram to slideacross that upper surface. As material is driven beyond positions inwhich it is in contact with the upper surface, it may remain softened(and susceptible to further bending) for a short period of time, or itmay cool and become only deflectable (rather than bendable or moldable).Whether cooled by movement past the heated portion(s) of the ram or byremoving the article from contact with the ram (or even by appliedcooling, such as by directing cool air at shaped portions, by using acooled plug element within the body of the article, or otherwise),cooling of the deflectable flange below its glass transition temperature“sets” or “locks in” the conformation of the material at the time ofthat transition. Thus, by shaping the deflectable flange so that it hasthe conformation shown in FIG. 8G and cooling it below its glasstransition temperature, the edge of the article can be rendered smooth(both because its bend region 150 is smooth and because its spacer 140,including its peripheral edge 110 have been changed to have aconformation in which no rough or sharp edges are present at theperiphery of the article.

As shown in FIG. 8F, the peripheral flange 120 can be partiallydeflected during shaping of the deflectable flange; in the finishedarticle, the peripheral edge preferably “points” toward the body or theunderside of the deflectable flange. As shown in FIG. 8G, shaping of thedeflectable flange will sometimes result in disappearance of theperipheral flange and the elbow interposed between it and the remainderof the spacer. This can occur because the material in the peripheralflange “melts” into the spacer or simply because the offset angle of theelbow becomes approximately 180 degrees. As can be seen in FIG. 8J, forexample, though, the peripheral flange 120 can deflect in a directionthat it remains distinct from the remainder of the spacer, potentiallyforming a hook-like structure. Because such a structure could positionthe potentially-sharp or -rough peripheral edge at or near the peripheryof the article, it is preferable that the deflectable flange bedeflected sufficiently that any such hook-like structure is containedwithin (relative to the periphery of the article) the rolled-over edge,as illustrated in FIG. 8K.

In the methods illustrated in FIGS. 1 and 8, impingement of the upperbody 200, the ram 300, or both upon the deflectable flange 160 caninduce inward flexing of the walls of the shaped article. By way ofexample, the compression induced in the deflectable flange uponimpingement upon the flange of the sidewalls of the upper body (comparethe positions of spacer 140 in FIGS. 1A and 1B) will induce inward(i.e., away from the sidewalls of the upper body and toward the shapedbody 10 of the article 100) force on extension 50, which force will betransmitted to the shaped body, potentially causing a portion of thebody to buckle or deflect. Similarly, impingement of the ram upon theperipheral flange portion 120 of the deflectable flange will also induceinward force on the extension and thereby upon the shaped body. Furtherby way of example, inward force exerted upon deflectable flanges inembodiments shown in FIGS. 7 and 8 can also be transmitted to the shapedbody of the article. Transmission of force from the deflectable flangeto the shaped body can be undesirable for at least two reasons. First,deflection of the shaped body can alter the orientation of thedeflectable flange and the portions that are bent as described herein,making control of the final shape of the article (and its edge)difficult. Second, force that is transferred from the deflectable flangeto the body will generally not drive the deflectable flange against theram and/or upper body, meaning that the force will not cause the bendingand deflection of the deflectable flange described herein, at least tothe intended degree. It is therefore desirable to limit transmission offorce from the deflectable flange, deflection of the shaped body by suchforces, or both, so as to direct the force into deflection of thedeflectable flange.

Substantially any equipment or method for preventing or reducingtransmission of force from the deflectable flange to the body, reducingor preventing deflection of the shaped body, or both can be employed.Shown in FIG. 8D is an example of such equipment and how it is used.FIG. 8D illustrates shaping of the deflectable flange 160 in a shapedarticle 100 by application of downward force (open arrow), as shown inFIG. 8B. In contrast with FIG. 8B, the shaped article shown in FIG. 8Dis coupled with three objects, 401, 402, and 403. Shown here incross-section, each of the three objects is a solid having a roundedsquare profile (e.g., rounded metal bars). Object 401 is abutted againsta portion of the shaped article 100 upon which inward force (smaller,horizontal solid arrow) is applied when the downward force causes thedeflectable flange 160 to impinge upon the upper surface 302 of the ram300. Object 403 abuts the extension 50 of the deflectable flange andtransmits the downward force to the deflectable flange. Object 402connects (rigidly, in this example, but not necessarily) objects 401 and402. One or more of the three objects can be cooled, to prevent heat(e.g., from heated ram 300) from softening the plastic at its body orextension.

In FIG. 8D, when downward force (open arrow) is applied to the object403, the force is transmitted to the deflectable flange. Impingement ofthe deflectable flange upon the ram 300 opposes the downward force. Thisforce could, in the absence of object 401 be transmitted through thedeflectable flange (i.e., through extension 50) to the shaped body ofthe article 100. However, because object 401 is present and held inplace sufficiently to prevent deflection of the portion of the articleit abuts, downward force applied to the deflectable flange cannot bedissipated by deflection of the shaped body (i.e., in the directionindicated by the small horizontal black arrow in FIG. 8D, because object401 prevents such deflection), and the downward force is instead imposedalong the deflectable flange in the direction shown by the large blackarrow in FIG. 8D. This force drives the deflectable flange (particularlyits peripheral edge, the peripheral flange if present, and the portionof the spacer nearest the peripheral edge) against the ram 300 andinduces deflection of the deflectable flange, conformation of portionsof the deflectable flange against the upper surface 302 of the ram(especially when the amount of heat provided by the ram is sufficient tosoften those portions), and displacement of the deflectable flangeacross the surface of the ram. As shown in the figure, the contour ofthe upper surface of the ram is thereby imparted to the peripheral-mostportions of the deflectable flange, resulting in smooth bending of thoseportions (assuming a smooth contour to the upper face of the ram) anddisplacement of the peripheral edge of the deflectable flange toward thebody of the article (or even ‘curled’ back beyond the body, for exampleas shown in FIG. 8C).

The shape, size, arrangement, attachments (if any) of objects 401, 402,and 403 are not critical. Likewise, not all three objects neednecessarily be used together; one, two, or all three can be employed. Inone embodiment, the three objects are fixed together to form a “lid” or“plug” for a container like that shown in FIG. 6, so that the portion ofthe lid/plug that corresponds to object 401 can substantially fill theinterior of the container (i.e., pressing against all walls, andespecially including the four long, straight walls of the container;see, for example, plug P in FIGS. 8Di and 8Dii), the portion of thelid/plug that corresponds to object 403 forms a ring that can be appliedagainst the entire rim of the container surrounding its interior, andthe portion of the lid/plug that corresponds to object 402 can be anymaterial or mechanism that connect them. For example, such a lid/plugcould be formed from a single piece of material (e.g., a ‘plug’ thatfills the entirety of the interior and overlaps the rim surrounding theinterior). One or more of the objects can be cooled to reduce heating ofthe shaped article (other than where desired, at portions of thedeflectable flange) and to thereby prevent undesired deformation of theshaped articles during processing.

Generalized, object 401 is simply a mass for preventing flexing of thesides of the shaped article during deflection of the deflectable flange.Such an object may fill substantially all portions of the interior ofthe shaped article (e.g., the entire interior of the container shown inFIG. 6D). Alternatively, one or more objects 401 may be used to buttressportions of the shaped article that are more easily deflected thanothers (e.g., the long straight sides of the container shown in FIG.6D).

Object 403 can be any object that can urge the deflectable flangeagainst the ram. Multiple objects can be used to urge the deflectableflange against one or more rams at various locations on the article, ora single object 403 that contacts the article at or near all portions ofthe deflectable flange can be used. In one embodiment, object 403 is theupper body 200 described herein, such as in the form that completelysurrounds the rim of a container such as that shown in FIG. 6D. Object403 can be a frame designed to fit snugly against the entire rim of acontainer surrounding an internal concave compartment of the chamber, soas to simultaneously urge a deflectable flange that completely surroundsthat rim against a ram in the manner described herein. In oneembodiment, object 403 can be deliberately cooled (e.g., by directing acooling fluid such as chilled water, chilled oil, or ambient air againstor through the object, particularly where the object is made of a goodconductor of heat, such as a metal) so as to reduce, inhibit, or preventheating of the body of the shaped article during processing (e.g., asshown in FIG. 8D). Object 403 can be linked, rigidly or movably, withobject 401 so that the flex-resisting object 401 can be applied to theinterior of a shaped article simultaneously with application of force tothe deflectable flange of the shaped article by object 403.

Object 402, when present, can be an object that connects object 403 to asource of force, an object that holds object 401 in place within aconcave portion of shaped article 100 during deflection of deflectableflange 160, or a combination of these.

As illustrated in FIGS. 9C and 9E, an additional advantage of therolled-over edge formed by this process is that the rolled edge can beused instead of conventional stacking lugs (i.e., thermoform-shapedportions of articles contoured to limit how closely an article can nestwithin another otherwise-identically shaped article). Such knownstacking lugs, in order to perform their desired anti-nesting function,must furthermore be narrower at their upper end than their lower end(referring to FIG. 9D as an example) in order to prevent nesting of thestacking lugs of adjacent trays. This ‘narrower-at-the-top’ conformationpresents known difficulties with de-molding the trays duringthermoforming, since the narrower ‘top’ portion of the lug must bestretched or deformed over the larger ‘bottom’ portion of the lug moldin order to remove the thermoformed tray from the mold. The rolled edgedepicted in FIGS. 8 and 9 (i.e., made as described herein) avoids thisdifficulty, while still preventing inappropriately close nesting ofadjacent trays. Trays having the rolled edge described herein can beseparated using conventional de-nesting equipment (e.g., screw- andfinger-based machines for separating adjacent nested/stacked trays) and,as shown in FIG. 9E, permit denser packing of trays than is possibleusing trays having formed stacking lugs.

FIG. 9F illustrates an optional embodiment of the rolled edge describedherein that also affects the stacking characteristics of shaped articleshaving the rolled edge. On the right side of FIG. 9F are shown threestacked trays having the rolled edge described herein, the rolled edgebeing substantially identical (including in height) about the entireperiphery of the tray. On the left side of FIG. 9F are shown three otherstacked trays, these trays also bearing a rolled over edge as describedherein about their entire periphery. However, in contrast to the trayson the right of the figure, the rolled edge of those on the left are notuniform about their entire periphery. As shown in the figure at onecorner, a smaller portion of the deflectable flange has been rolled overat the corners of these trays than the portion of the deflectable flangethat is rolled over along other portions of their edge. As a result, thetrays bear rounded stacking extensions 180 at their corners. Like thatstacked trays shown on the right of FIG. 9F, those on the left of thefigure are nested within one another and settle until the lower surfaceof the rolled edge of a tray contacts and rests upon the upper surfaceof the rolled edge of a second tray within which it is nested. However,because the stacking extensions 180 of the trays on the left of thefigure have a greater height than much of the rest of the rolled edge ofthose trays, the trays on the left will nest such that the lower surfaceof a stacking extension 180 rests on the upper surface of the rollededge of a tray beneath it, leaving the lower surface of much of therolled edge of the upper tray out-of-contact with the tray beneath it,yielding a gap between the nested trays (compare the gap indicated bythe large brackets in the left of FIG. 9F with the indentation indicatedby the small brackets in the right of FIG. 9F). When a shaped article100 is given a rolled over edge including a stacking extension 180 asdescribed herein, the degree to and way in which the deflectable flangeis deflected should nonetheless be selected to position the peripheraledge 110 at the stacking extension 180 such that it is unlikely tocontact films or other materials at the periphery of the article 100, asdescribed herein.

Yet another advantage of the ‘rolled edge’ depicted in FIGS. 8 and 9 isthe mechanical strength imparted to a shaped article by such an edgeconformation. Thin plastic films tend to be highly flexible, andarticles formed from such films can have ‘flimsy’ edges that are easilydeformed upon handling or manipulation (e.g., during sealing or wrappingwith film). For the same reasons that hollow tubes or rounds of materialtend to be stronger and more rigid than planar sheets of material of thesame type and thickness, the curved or rolled edge described hereinconfer greater edge strength and rigidity to the shaped articlesdescribed herein than corresponding articles lacking such an edge. Thisedge strength and rigidity permits formation of lids upon, or engagementof separately-made lids with shaped articles described herein. Thus, inaddition to the shaped articles being sealable with film using OW, VSP,or MAP technologies, the enhanced edge strength of the shaped articlesdescribed herein permits them to be sealed with snap-on/snap-off typelids or other conventional sealing technologies. The edge strength andrigidity conferred to the shaped article also prevents deflectioninduced by tension in a film used to overwrap or seal the article (e.g.,so-called “bow-tying” as the phenomenon of a concave article closingupon its concavity when wrapped or sealed) and to withstand stressesimposed by (or necessary to the operation of) container-handlingequipment, such as de-nesting equipment used for segregating individualcontainers from a stack of nested containers.

As noted above, the edge strength and rigidity observed in shapedarticles (e.g., trays for wrapping or sealing with thin films) made asdescribed herein derives from the geometry and materials present in thearticle edge. Those geometry and materials, in turn, derive from thegeometry and materials selected for use in the deflectable flangedescribed herein. Although it is believed that many of the followingcharacteristics are immediately apparent to skilled workers in thisfield, these characteristics are discussed in the context of selectingthem to affect the edge strength and rigidity. One such characteristicis the thickness of the thermoplastic used to form the edge. All elsebeing equal, a thicker polymer sheet tends to be more difficult to flexor deform than a thinner one; as a result the edge strength and rigidityof articles described herein can be increased by employing thickerthermoplastic—either by thermoforming a thicker initial sheet or bythickening the thermoplastic during edge-rolling (e.g., by intraplanarcompression of the sheet in its softened state or simply by maintainingit for a longer time in its softened state). The radius of curvature ofthe bent region of the shaped article can also affect edge strength andrigidity, with smaller radii generally yielding greater edge strengthand rigidity. The degree to which the peripheral edge 110 and adjacentportions (e.g., the spacer 120) of the deflectable flange are turned orrolled can also affect edge strength and rigidity. By way of example,rolling the edge into an essentially complete circle (i.e., rolling itabout 360 degrees, so that the peripheral edge 110 contacts theunderside 161 of the spacer 120) will yield substantially greaterstrength and rigidity than an edge that is rolled about 180 degrees(e.g., as shown 9B). Edge strength and rigidity can also be increased byincreasing the width of the extension 50 region that surrounds theconcave portion, or by forming the sidewalls of the concave portion toresist deflection (see, e.g., the “ribs” formed in the sidewalls of thecontainer shown in FIGS. 6C and 6D).

In one example, a standard sized tray suitable for MAP sealing was madeas described herein (i.e., by giving it a rolled-over edge) and comparedwith a similar tray made of the same material, but lacking the rollededge. The edge strength/rigidity of the two trays was measured byassessing the compressive force required to achieve ¼ inch deflectionwhen each of the trays was compressed at the mid-points of the opposedlong edges of the trays. The tray having the rolled edge describedherein was found to require (roughly 5.5 pounds of force required forthe rolled-edge tray and roughly 2.3 pounds of force required for thenon-rolled-edge tray), demonstrating an example of substantialedge-strengthening. While it is not practical to describe every possiblecombination of configuration, dimension, and material selection thatwill yield a desired edge strength or rigidity, a skilled artisan inthis field is able to use the information provided herein to designarticle edges having a wide range of strengths and rigidities superiorto those of articles lacking the deflected-edge described herein. Theedge strength and rigidity of the articles described herein is importantfor resisting compressive forces occurring when sealing packages, whenpressurizing or evacuating the interior of the concave portion duringpackaging, and combinations of these. This edge-strengthening effecttherefore represents a significant advance in packaging function.

What is important in these methods is that the potentially sharpperipheral edge 110 of the thermoplastic sheet(s) from which the article100 is formed should be deflected away from the periphery of the articleand ‘frozen’ in that position by heat-softening and cooling a portion ofthe sheet that is bent (which will normally include substantially onlyportions of the deflectable flange) while the sheet is so deflected. Theheated, bent, and cooled region preferably includes at least the bendregion 150 of the deflectable flange 160, because that region isdesigned for smooth flexing and yields a smooth periphery to thecontainer. Softening, flexing, and hardening of other portions of thedeflectable flange (e.g., the extension 50, spacer 140, elbow 130,and/or peripheral flange 120) can also (or alternatively) be done, andcan contribute to smoothness of the article's periphery.

Alternatively, any of these portions of deflectable flange 160 cansimply be bent without heating, so long as sufficient bending force isapplied that the thermoplastic material irreversibly bends (rather thanmerely reversibly deflecting upon removal of pressure) at the bentlocation. However, non-heating-and-softening-based bending methods willtend to leave relative sharp (or, at least, less smooth) edges wherebends are imposed, and so such methods are not favored unless care istaken (e.g., by bending materials about a rounded ‘mold’ member) toensure that such bends are smooth. The deflectable flange 160 disclosedherein provides a convenient structure for practicing this method.

The Deflectable Flange 160

The deflectable flange includes a bend region 150, a peripheral edge110, and a spacer 140 interposed between the two. The bend region formsan angle of less than 180 degrees between the body 10 and the spacer 140and functions as a flexible ‘hinge’ at which the spacer region can bedisplaced relative to the body. The angle formed by the bend region(i.e., the angle designated A in FIG. 1A) is preferably about ninetydegrees (i.e., approximately a right angle, meaning not less than 75 normore than 105 degrees, more preferably not less than 85 nor more than100 degrees, still more preferably not less than 87 nor more than 93degrees, and most preferably about 92 degrees). When this angle is lessthan 90 degrees, it can be difficult to remove the thermoformed articlefrom the thermoforming mold (i.e., because the portion of the moldnearest the extension between the spacer and the body can be broaderthan the width between the body and the spacer nearer to the peripheraledge, meaning that the thermoformed article will ‘grip’ the mold andmust be pulled or expanded to displace it from the mold). Thus, it ispreferable that the angle formed by the bend region is 90 degrees orgreater (e.g., 91, 92, 93, 94, or 95 degrees) to ease separation of thethermoformed article and the mold, but the angle can be smaller if thebody of the article recedes away from the periphery, for example. Lesspreferably, an angle of 110, 115, 120, 125, 130, or 135 degrees can beemployed, but such articles may require application of both an upperbody 200 to reduce the angle near to 90 degrees prior to impacting thedeflectable flange against the ram 300. As this angle increases, theamount of thermoplastic that is present at exterior corners (e.g., thefour corners of the tray shown in FIGS. 6A and 6B) of the thermoformedprecursor article increases and can interfere with bending (i.e.,“rolling-over”). This thermoplastic material can be accommodated, forexample, by permitting the spacer to ‘bow out’ above the ram (or into aspace built into the upper surface of the ram) at sections where thematerial occurs.

Upon sufficient displacement of the spacer, the bend region forms theperiphery of the article (i.e., when the spacer is bent “under” theconnected portion of the body, regardless of orientation relative togravity). Thus, the bend region will normally form the smooth peripheryof the article that is desired in one embodiment. The spacer nonethelessforms a part of the periphery of the article in this embodiment(normally the “underside” of the periphery, relative to the article 100,with the underside 161 of the deflectable flange 160 being containedwithin the curvature of the rolled-over edge). For this reason, portionsof the spacer (potentially including the elbow 130 and the peripheralflange 120) that are reasonably accessible to a film or other materialpressed against the exterior of the article (e.g., against the undersideof its periphery) should preferably be smooth as well.

In formation of the shaped articles with a smooth periphery describedherein, deflection of the spacer (and/or other portions) of thedeflectable flange induces bending within the bend region, within thespacer, or both. The angular shape of the bend region both controls thelocation of that bending and the smoothness of the resulting edge. Asillustrated in FIGS. 1 and 8, it can be beneficial if the angularportion of the bend region is not formed as a sharp (i.e., bi-linear)angle, but is instead formed as flat portions (e.g., an extension 50 anda spacer 140) arranged at an angle to one another, with a curved portion(e.g., defined by a radius of curvature, such as a radius of 1, 2, or 3or more millimeters) connecting the flat portions. Flexing of a curvedangular portion will tend to yield a smoother, less film-damaging edgethat flexing of a sharply angled portion. As illustrated in FIGS. 1, 4,5, 7, and 8, the boundary between the bend region 150 and the spacer 140may be substantially indistinguishable in practice, and flexion of thespacer 140, at least at its extent nearest the bend region 150 isexpected in the embodiments shown. As illustrated in FIG. 8 especially,bending of multiple portions, including the peripheral-most portion(s),of the spacer 140 can desirably impart a smooth periphery to thearticles prepared as described herein.

In one embodiment (shown in FIG. 1), the deflectable flange 160 includesat least three portions, including the bend region 150, a peripheralflange 120, and an elbow 130 positioned therebetween. The bend region150 is connected to the remainder of the article 100, optionally by wayof an extension 50. The peripheral flange 120 is connected to the bendregion 150 by way of the elbow 130, optionally with a spacer 140interposed between the bend region 150 and the elbow 130. A prototypicaldeflectable flange 160 having each of these portions is illustrated(attached to the body 10 of an article 100) in FIG. 1A.

In this embodiment, the bend region 150 is situated anti-peripherally(nearer the body 10) than at least the peripheral-most portion of theperipheral flange 120. The function of the bend region 150 is to deflectwhen the peripheral flange 120 is deflected inwardly (i.e.,anti-peripherally, such as by pressing the periphery of the articleagainst a solid object). Deflection of the bend region provides a smoothsurface because the peripheral edge 110 of the thermoplastic sheet isnot located within the bend region; it is located on the peripheralflange 120. The angle formed by the bend region (for example,approximately 90 degrees over the bend region 150 shown in FIG. 1A) isnot critical, and can be selected for ease of manufacture. It can, forexample, be an obtuse angle, a right angle, or even an acute angle. Whenthis angle is an acute angle, it can be difficult to remove thethermoformed (pre-roll-over) article from its thermoforming mold(because the peripheral portion of the spacer must be deflected toremove the article from the mold), and acute angles are disfavored forthat reason (even though such articles can still be made). The radius ofcurvature of the bend region 150 is also not critical, although it ispreferably substantially greater than the radius of curvature of theelbow 130.

The bend region 150 preferably has the conformation of a smooth curve,as shown in FIG. 1A, with a substantial radius of curvature (e.g., 0.5millimeters to several millimeters or more), so that inward deflectionof the deflectable flange 160 yields a smooth periphery to the article.However, it is critical that the bend region 150 simply not be sharp orpointed; a non-sharp crease can suffice, for example. Fragile materials,such as thin plastic films or animal skin, which contact that smoothperiphery are much less likely to be damaged than when the same fragilematerials contact the peripheral edge 110 of the thermoplastic sheet.

The bend region 150 can be connected with the remainder of the article100 by way of an extension 50. The extension 50 can be discretelydiscernible from the bend region 150 (e.g., a flat region distinct froma curved bend region 150) or substantially indistinguishable (e.g., aslightly curved region not readily distinguished from the curvature ofthe bend region 150). The dimensions of the extension region are notcritical; it can range from non-existent (i.e., the bend region 150commences at the edge of a body 10 of the article 100), to a fraction ofa millimeter, to several millimeters or longer. One function of theextension 50 is to separate the bend region 150 (at whichsheet-softening heat is applied in some embodiments) from other portionsof the article 100 at which potential heat-induced deformation isundesirable. Another function of the extension 50 can be to provide afunctional surface to the article 100, such as a surface adjacent thebend region 150 at which a thin plastic film (which can be pressedagainst the bend region 150 with little danger of damage to the film)can be adhered to or fused with the article 100 (e.g., to cover a cavityformed in the article that is bordered by the deflectable flange 160 ofwhich the extension 50 is part). The extension 50 can also serve astructural function, such as providing support or rigidity to a sectionof the article (e.g., by forming a relatively rigid “rim” about a cavityin a container to inhibit flexing of the container while lidding isapplied). Yet another function of the extension 50 can be to provide aspace which the deflectable flange 160 can occupy when it is deflectedanti-peripherally. Because the extension 50 and the peripheral flange120 are situated on opposite sides of the bend region 150, sufficientflexing of the bend region 150 (e.g., upon insertion of the article 100within the upper body 200 and insertion of the ram 300 behind thearticle), the spacer 140, or both, can cause the peripheral flange 120(and the spacer 140) to approach, or even contact, the extension 50, orto curl or deflect beneath the extension 50 between the periphery of thearticle and a sidewall of the body of the article (see, e.g., FIG. 6E).

In an important embodiment, shown for example in FIGS. 3A, 3B, and 6E,flexion of the bend region 150, the spacer 140, or both, followed bycooling and rigidification yields an article in which a gap occursbetween the sidewall of the body of the article and the nearest approach(i.e., closest extent) of the bent portion of the deflectable flange.The size and position of this gap can be selected by selection of theshape of the body, placement of the ram 300, the shape of the uppersurface 302 of the ram 300, or a combination of these. The gap can beselected to extend entirely about the perimeter of the article, forexample, so that the article has a rolled-over edge completely about itsperiphery, with a gap adapted to fit a predetermined shape (e.g., aMAP-sealing apparatus designed to engage a standard sized tray, such asan industry-standard #3 tray, for example). The size and position ofthis gap are not critical and can, for example, be selected to have awidth and position that mirrors the width and position of a flat portionof the extension 50 (e.g., a flat sealing surface carried on theextension) or a fraction thereof. By way of example, when the extension50 bears a flat sealing surface on its upper (opposite the concavity)face, the rolled-over edge can be formed to leave a gap on the lowerface of the extension 50 that parallels and has a width of one-half orthree-quarters the width of the sealing surface on the opposite face.Alternatively, the article and its edge-rolling or -deflecting processcan be selected to yield a gap having a substantially constant width(e.g., a gap of ⅛, ¼, or ½ inch) completely around the sidewalls of theconcave portion on the underside of the extension 50.

The shaped articles described herein can be made to conform to theshape, size, dimensions, colors, and any other characteristics of trayscommonly or exclusively used with particular equipment. Numerous“industry standard” trays are known, such as MAP trays commonly referredto simply as “Number 2,” “Number 3,” “Number 4,” and “Number 11,” forexample, and these MAP trays have conserved dimensions and shapes thatare essentially uniformly conserved across the industry. Adaptation ofthe shaped articles described herein to match the size, shape,dimensions, colors, and other characteristics of industry standardequipment is generally within the ken of a skilled artisan.

In FIG. 1A, the peripheral flange 120 includes the (potentially sharp)peripheral edge 110 of the thermoplastic sheet(s) from which the articleis formed. It extends peripherally beyond the bend region 150, so thatit will impinge upon the inner surface 202 of the upper body 200 whenthe article is inserted into the cavity of the upper body 200, as shownin FIG. 1B. It extends from the elbow 130 to that peripheral edge 110and extends in a direction from the bend region 150 or the spacer 140,if present, by an offset angle defined by the elbow 130. The function ofthe peripheral flange 120 is to engage with (i.e., impinge upon or beimpinged upon by) the inner surface 202 of the upper body 200 when thearticle is inserted into the cavity of the upper body 200, therebycausing the deflectable flange 160 to deflect inwardly(anti-peripherally). In addition to displacing the peripheral edge 110of the sheet anti-peripherally and causing flexing or bending of thedeflectable flange 160 in the bend region 150 thereof, this deflectionalso positions the peripheral flange 120 to be further anti-peripherallydeflected when the ram 300 is inserted into the cavity behind thearticle 100. When the ram 300 is so inserted, it impinges upon theperipheral flange 120 and, upon further advancement of the ram into thecavity, causes both additional flexing or bending of the deflectableflange 160 in the bend region 150 thereof, and additionalanti-peripheral deflection of the peripheral edge 110.

The length (elbow-to-peripheral-edge) of the peripheral flange 120 isnot critical, but should be selected to facilitate engagement of the ram300 by the peripheral flange 120 and displacement of the peripheralflange 120 by the ram 300 as the ram advances within the interior of theupper body 200. Frequently, the length of the peripheral flange 120 isinfluenced, at least in part, by the ability to cut articles from amaterial in which the article is formed. The elbow 130 can function, inpart, to position the thermoplastic sheet at a location at which it canbe conveniently cut to free the shaped article from a precursor sheet.Because the peripheral edge 110 formed by such cutting is a source ofsharpness or roughness at the periphery of the article prior to ‘rollingover’ the deflectable flange 160, it can be beneficial to cut the sheetas near to the elbow 130 as possible (i.e., to make peripheral flange120 as small as possible) so as to reduce the bulk of thermoplasticmaterial that must be displaced in order to displace the sharp or roughperipheral edge 110 from the periphery of the article. As illustrated,for example, in FIG. 8H, a larger peripheral flange also reduces contact(and increases spacing) between the upper surface of a ram whichimpinges the deflectable flange, and therefore reduces heat transferfrom the ram to peripheral portions of the deflectable flange. Becausethe methods described herein depend upon heating those portions abovetheir glass transition temperature, deflecting them to a desiredconformation, and then cooling the portions below that temperature,larger peripheral flanges increase the heat input and/or time requiredfor such processing and are disfavored for that reason as well.

The elbow 130 is interposed between the bend region 150 and theperipheral flange 120, and its function is to connect and transferforces between them. That is, compressive forces applied to theperipheral flange 120 by impingement thereupon by the upper body 200 orthe ram 300 are translated through the elbow 130 (and the spacer 140, ifpresent) to torsional force applied to the bend region 150. Thistranslation of compressive force to torsional force ensures that thebend region 150, the spacer 140, or both flex when force is applied tothe peripheral flange 120. Thus, application of force to the peripheralflange 120 by the upper body 200 and/or ram 300 both deflects theperipheral edge 110 anti-peripherally (i.e., displacing the potentiallysharp edge away from the periphery of the article) and induces bendingof the bend region 150, the spacer 140, or both (i.e., yielding a smoothperiphery formed by flexed thermoplastic sheet at the periphery of thearticle), yielding an article which has a smooth periphery, even if thearticle was formed by a process that yields a sharp peripheral edge atan intermediate step. In effect, the elbow causes forces applied to theperipheral flange 120 to induce the deflectable flange 160 to “rollover” the periphery of the article, effectively “hiding” the sharp edgeof the thermoplastic sheet from materials at the periphery of thearticle.

A spacer 140 can be interposed between the bend region 150 and the elbow130. The spacer 140 can be discretely discernible from the bend region150 (e.g., a flat region distinct from a curved bend region 150) orsubstantially indistinguishable (e.g., a slightly curved region notreadily distinguished from the curvature of the bend region 150). Thedimensions of the extension region are not critical; it can range fromnon-existent (i.e., the bend region 150 commences at the elbow 130), toa fraction of a millimeter, to a few millimeters or longer. One functionof the spacer 140, if present, is to act as a ‘lever’ by which forceapplied at the elbow 130 (e.g., by impingement between the peripheralflange 120 and one or both of the upper body 200 and the ram 300) istransmitted to the bend region 150. Another function of the spacer 140,if present, can be to position the peripheral flange 120 suitably toengage one or both of the upper body 200 and the ram 300. Yet anotherfunction of the spacer 140, if present, is to increase the distance bywhich the potentially sharp peripheral edge 110 of the thermoplasticsheet can be displaced anti-peripherally from the periphery of thearticle upon flexing of the bend region 150. All else being equal, thelonger the spacer 140 is, the farther from the article's periphery thatpotentially sharp edge will be when the article is made as describedherein. A deflectable flange including the spacer 140, but lacking theelbow 130 and peripheral flange 120 can be used, as shown for example inFIGS. 8A-8D.

A longer spacer 140 facilitates formation of one or more portions of the“rolled edge” that is taller than other “rolled” portions of the edge,yielding a structure useful as a stacking lug (e.g., to facilitateselectable spacing between the rolled edges of adjacent nested, stackedarticles). In one embodiment, the size of the spacer and the compressiveforce applied to the spacer (i.e., the force transmitted to the spacerfrom the extension region, balanced by resistive force applied to thespacer on account of its impingement upon the ram) can cause the spacerto flex outwardly (i.e., peripherally away from the body of thearticle), forming a smooth bulge that, upon cooling, forms the outerperiphery of the article.

Regardless of whether the bend region 150, the spacer 140, or both arebent in the operations described herein, and further regardless ofwhether material that was originally part of the bend region 150, thespacer 140, or both ultimately form the outer periphery of the articlesdescribed herein, what is important is that that outer periphery be free(or, less favorably, substantially free) of sharp, pointed, rough, orabrasive edges that might damage thin plastic films, human tissues, orother fragile materials which might contact that outer periphery.

Thermoplastics

The methods and articles described herein can be performed and made withsubstantially any thermoplastic material. What is important is that thematerial be capable of being softened by heating and re-stiffened uponcooling, at least in the deflectable flange 160 described herein.Substantially all thermoplastics exhibit a characteristic temperatureabove which they soften and become flexible or workable and below whichthey become more rigid and retain their shape. Desirable thermoplasticsfor the articles and methods described herein retain their shape undernormal conditions of the anticipated end use of the container. It isalso desirable to use thermoplastics which can be softened underconditions that are readily attainable in a manufacturing environments.Examples of suitable thermoplastics include polyethylene (PE),polypropylene (PP), polyethylene terephthalate (PET), and polyvinylchloride (PVC). Other suitable thermoplastics are apparent to skilledworkers in this field, and substantially any of these can be used. Alsopotentially useful are flexible plastics having deformable materialssuch as metal foils bound to their surface.

The thermoplastic article includes a thermoplastic material, includingat at least the portions of the article at which the deflectable flange160 described herein is formed or present. The identity of thethermoplastic material is not critical, nor is the presence or absenceof non-thermoplastic materials. Where non-thermoplastic materials arepresent (e.g., in a thermoplastic sheet to which a metal foil or apaperboard layer is laminated), the rigidity imparted to the article bythe thermoplastic material in its non-softened, non-molten state ispreferably sufficient to define the conformation of the article, evenwhen the non-thermoplastic material is bent. The article can include oneor more peelable layers, for example as described in co-pending U.S.patent application Ser. No. 13/415,781. When one or more peelable layersis present, it is substantially unimportant whether those layers are“rolled over” at the peripheral edge of the shaped article (rather thanthe edges of the peelable layers peeling from the underlying substrate).Both for aesthetic reasons and to promote sealing, it can be preferablethat any peelable layers remain adhered. When peelable layers arepresent and adherence is to be promoted, the working temperature shouldbe selected both to be suitable for deflection of the deflectable flangeas described herein and for working the substrate and peelable layers ofthe shaped article without causing delamination of the peelable layers.

In an important embodiment, the thermoplastic selected to make theshaped article is optically clear (i.e., transparent, preferablypermitting transmission therethrough of >50% of light of wavelengths inthe human-visible range, and preferably permitting such transmissionwithout substantial distortion). Clear packaging materials are preferredfor many products (e.g., meats and fish, vegetables, and prepared meals)which are sold directly to consumers. Clear packaging permits directvisual inspection of package contents prior to purchase. Prior to thisdisclosure, it was difficult or impossible to manufacture a shapedarticle (e.g., a tray for containing food) that was both optically clearand suitable for sealing with filmusing all three of the OW, VSP, andMAP technologies. OW sealing was commonly used with blunt-edged trays,and the bluntness (i.e., non-sharpness) of the edges was achieved byusing foamed plastic materials, such as Styrofoam. Trays made of clearmaterials were generally not suitable for at least OW sealing with thin,fragile plastic films. VSP and MAP trays have typically been made ofpolypropylene materials which are seldom, if ever, optically clear.

For optically clear shaped articles as described herein, a variety ofoptically clear plastics can be used. PETs, PVCs, and polycarbonates,for example, are suitable. The shaped article should be optically clearat least in the concave portion in which contents are intended to bestored, and are preferably clear throughout the deflectable flangeadjacent that portion, including any bend portion 160 and any portionthat is bent during the operations described herein. For this reason,clear thermoplastic trays, such as those made of PET or PVC arepreferably employed, and any heating or bending conditions imposed uponthose trays during manufacture are preferably selected so as not toinduce development of opacity in the materials (e.g., by heating above asoftening temperature before flexing them).

The Upper Body 200

The upper body 200 performs a number of functions. Overall, its functionis to contain the deflectable flange 160 described herein within acavity in the upper body 200 while heat is applied to one or moreportions of the bend region 150 thereof. This containment function canprevent non-desired deformation (or guide desired deformation) of thedeflectable flange 160 or portions of it during the periphery-smoothingoperations described herein. The shape of the interior cavity of theupper body 200 can also affect the shape of the deflectable flange as itbends, particularly as it is softened. By way of example, in FIG. 1B,the upper body 200 includes a cavity with an internal right angle intowhich a portion of the bend region 150 is forced; the right-angle shapeof this portion of the cavity will tend to cause the bend region 150 toconform to a right-angle shape, especially as the bend region 150softens. The heat source can be a part of the upper body 200, applied tothe upper body 200 for conduction of heat therethrough, for example. Theupper body 200 also impinges upon and is impinged upon the peripheralflange 120 of the deflectable flange 160 when it is inserted into thatcavity. When a ram 300 is used, the upper body 200 also serves toprevent the deflectable flange 160 from being forced out of the cavity,and it can also limit deflection of the bend region 150 when thedeflectable flange 160 is being compressed by the ram 300.

The materials from which the upper body is constructed are not critical,other than that they should be suitable to withstand the manufacturingconditions described herein. That is, they should not melt or degrade atthe temperatures used in the processing. A wide variety of metal,ceramic, stone, and polymeric materials can be used.

It is important that the shape of the upper body 200 be selected so thatimpingement between the interior of the cavity in the upper body 200 andthe peripheral flange 120 will occur when the article 100 describedherein is inserted into the cavity in the upper body. The upper body canhave a shape sufficient to simultaneously impinge multiple peripheralflanges 120 on an article, or to impinge upon most or all of a singleperipheral flange 120 that occurs upon an article (e.g., one whichoccurs about the entire peripheral edge of an article). As illustratedin FIG. 2, the upper body 200 can be formed of a solid block of materialthat covers an entire face of an article while impinging peripheralflange(s) 120 that occur on one or more portions of the article. Theupper body 200 depicted in FIG. 2, for example, is designed to impingeupon the single peripheral flange 120 that extends completely around theperiphery of an article having the shape of a rectangular tray-typecontainer having rounded corners.

The bend region 150 of the articles described herein will typically bewithin the cavity of the upper body 200 when heat is applied to thatbend region 150. For that reason, the upper body should be constructedin a way that facilitates application of such heat. The upper body 200can, for example, include a heat source (e.g., electrically operatedheating plates or rods) within it, applied to it, or fluidly connectedwith it. Alternatively, the upper body 200 can include one or more portsthrough which a heated fluid (e.g., a heated gas or liquid) can passfrom a source into the interior of the cavity therein. The methodselected to deliver heat to the bend region 150 (and/or other portionsof the peripheral flange, such as the spacer 140, the elbow 130, and theperipheral flange 120) is not critical, and any of a variety ofwell-known heat delivery methods and equipment can be used. If the upperbody 200 is able to conduct heat and is cooled, then heat that ispresent in the deflectable flange 160 during its shaping can flow to theupper body 200, and this heat flow can serve to cool and thereby stiffenthe deflectable flange 160 in its deflected position upon itscompression between the upper body 200 and the ram 300, for example.

As shown, for example in FIGS. 5 and 8, the deflectable flange can bedeflected using a ram 300 alone, with or without use of an upper body200. The upper body can be used both to partially deflect thedeflectable flange and to apply force to the article so as to impingethe deflectable flange thereof against the ram. When the upper body 200is not used, some alternate means of applying force to the article tocause impingement between the ram and the deflectable flange must beused. In FIG. 8D, for example, this alternate means is depicted simplyas object 403 (optionally coordinated with object 402). The orientationof the parts relative to gravity is not important, the “downward” force(open arrow in FIG. 8D) need only be directed so as to urge thedeflectable flange 160 against the ram 300 to cause impingement betweenthe two. It is also immaterial to which of the article and the ram (orboth) force is applied in order to cause such impingement. What isimportant is that impingement of the deflectable flange 160 against theram 300 (and/o the upper body 200, if used) induces deflection of theperipheral edge 110 of the deflectable flange to a position where it isnot readily accessible at the periphery of the article. Thus, in oneembodiment, the upper body 200 can be a simple flat plate which can beapplied against a flat portion (e.g., the extension 50 of thedeflectable flange 160 depicted in FIG. 8D) of the article to drive thedeflectable flange in the direction of, and ultimately against, the ram.

The Ram 300

The primary function of the ram 300 is to induce deflection in thedeflectable flange. The ram can be used with or without a correspondingupper body 200, but such an upper body can serve to contain and controlthe article as it is contacted with the ram. The method and mechanism(s)used to impart relative motion between the article and the ram are notcritical. When an upper body is employed, the ram is used to impingeupon and apply compressive force to the peripheral flange 120 of thedeflectable flange 160 when the article is disposed in the upper body200. This compressive force tends to drive the peripheral flange 120upwardly toward the bend region 150 and the extension 50, if present,and anti-peripherally, thereby moving the potentially sharp peripheraledge 110 of the thermoplastic sheet away from the periphery of thearticle so formed. Accordingly, the design of the ram 300 is notparticularly critical, so long as such compressive force is applied. Asillustrated in FIGS. 1C and 4, a ram 300 having an angled upper face 302will tend to direct the peripheral flange 120 in the direction alongthat angle as it compresses the peripheral flange 120. Thus, it can bebeneficial to shape the upper face 302 of the ram 300 in a conformationthat deflects or “pushes” the peripheral flange 120 and/or theperipheral edge 110 anti-peripherally as compression occurs.

Like the upper body 200, the materials from which the ram 300 is madeare not critical. Metals, ceramics, stones, and polymeric materialscapable of withstanding the temperatures and pressures of operation aresuitable and readily selectable by a skilled artisan. If the ram 300 isable to conduct heat and is cooled, then heat that is present in thedeflectable flange 160 during its shaping can flow to the ram 300, andthis heat flow can serve to cool and thereby stiffen the deflectableflange 160 in its deflected position upon its compression between theupper body 200 and the ram 300, for example. Heat can likewise beprovided by the ram 300 to one or more portions of the deflectableflange in conventional ways, such as by using a heated ram orincorporating a heating element into or onto the ram.

In an embodiment illustrated in FIG. 2, a single ram 300 can beconstructed to impinge upon substantially all peripheral flanges 120 ofan article simultaneously. The ram 300 depicted in FIG. 2, for example,is designed to impinge upon and apply compressive force to the singleperipheral flange 120 that extends completely around the periphery of anarticle having the shape of a rectangular tray-type container havingrounded corners.

In an alternative embodiment illustrated in FIG. 5, the deflectableflange 160 of an article is heated to softening and impacted against aram 300 in the absence of an upper body 200 of the type describedherein. The absence of an upper body 200 may lead to distortion ordeflection of softened portions of the deflectable flange 160, at leastif the other portions (e.g., the extension 50 or parts of the body 10 ofthe article 100 that are adjacent the deflectable flange 160 areinsufficiently rigid to prevent such distortion or deflection. However,if such rigidity is present, or if such distortion or deflection istolerable in the final product, the methods described herein can be usedwithout an upper body 200.

FIG. 5 also illustrates the significance of the length (measured fromthe elbow to the peripheral edge) of the peripheral flange. Theperipheral edge contacts the ram. Force imparted upon the peripheraledge by the face 302 of the ram induces deflection of the deflectableflange 160 toward the body 10 of the article 100. When the deflectableflange 160 includes a peripheral flange 120 that is offset from thespacer portion 140 by a ninety-degree elbow 130, as shown in FIGS. 5Aand 5B, the length of the peripheral flange will influence the degree ofdeflection of the deflectable flange. Comparing FIG. 5C (a deflectableflange in which the “length” of the peripheral flange is zero; i.e., adeflectable flange lacking a peripheral flange) with FIG. 5B, it can beseen that the presence of the peripheral flange induces greaterdeflection of the deflectable flange in the configuration shown.Moreover, looking to FIG. 5A, increasing the length of the peripheralflange increases the degree of deflection induced by the ram. Thus,although the elbow and peripheral flange are optionally not present,their presence enhances deflection and can enhance the “rolling” effectthat can be achieved.

FIG. 10 depicts an embodiment of the ram 300 described herein forrolling over the edge of a shaped article having a deflectable flange160. FIG. 10A depicts a ram 300 having at least two positions foraccepting articles 100 having deflectable flanges as described herein.The upper portion of the figure shows a position that bears an article100. Because it does not bear an article, the position partially shownin the lower right of the figure reveals the upper surface 302 uponwhich the article is borne when present. The position in which anarticle is borne in the figure has an identical upper surface 302, butit is obscured by the spacer 140 and peripheral flange 120 of thearticle 100 borne therein. This figure also illustrates how theextension 50 spaces the body 10 of the article away from the spacer andaway from the ram, providing space (visible through the clear materialthat forms the extension) into which the spacer and peripheral flangecan be deflected, bent, or curled.

FIGS. 10B and 10C show details of the upper surface 302 of the ram 300,including a curved portion (at approximately D in FIG. 10C) which willdeflect the peripheral edge 110 of the deflectable flange when urgedagainst it at a softened temperature. FIG. 10B is a close-up image ofthe upper surface, and FIG. 10C is a cross-sectional diagramillustrating the approximate shape of that upper surface. In operation,the ram is used by impinging the peripheral edge 110 of the deflectableflange against the upper surface 302 (from the ‘downward’ directionindicated by the open arrow in FIG. 10C) at a position anywhere betweenpositions B and D, and then applying further downward force to drive theperipheral portion of the deflectable flange further against the ram.This further force induces the peripheral edge to slide, scrape, or skipacross the upper surface and induces the deflectable flange to deflectinwardly (i.e., toward the body of the article which, in thisembodiment, is located closer to the E position than to any of A-D).When the deflectable flange is heated above its softening point (i.e.,glass transition temperatures), this deflection will be non-elastic andwill be reflected in the shape of the deflectable flange if it isthereafter cooled to a temperature below its softening point.

The curved portion of the upper surface 302 of the ram 300 betweenpositions C and E in FIG. 10C induces the softened portion of thedeflectable flange to roll or curve, and the degree of curvature inducedis controlled by the extent to which the deflectable flange is impingedagainst the ram. Thus, for example, only the peripheral-most portion ofthe deflectable flange might be deflected if the deflectable flange iscaused to impinge only slightly against the upper surface aftersoftening, the peripheral edge will be pointed approximately toward thebody if a softened portion of the deflectable flange is impinged to theextent of position D, and the peripheral edge of the deflectable flangewill be effectively “rolled over” (i.e., the plane of the deflectableflange at its peripheral edge extends to intersect the underside 161 ofthe deflectable flange) if a softened portion of the deflectable flangeis impingingly extended beyond position D (as shown in FIGS. 8G and 8K,for example). Depending on the material from which the deflectableflange is made, the deflectable flange can substantially retain itsshape as it cools in the ‘rolled over’ configuration (e.g., PET and PVCmaterials tend not to slump or droop when acted upon by gravity in asoftened state, while PE and PP materials can be bent substantially bygravity alone when softened). Even when this is not so, so long as theperipheral edge of a deflectable flange that droops or slumps does notexpose the peripheral edge at the periphery of the article, such bendingis acceptable (e.g., when the rolled-over edge is rolled oversufficiently that any drooping occurs in the interior space of theroll).

Sealing Films

An important advantage of articles having peripheries treated in themanner described herein is that such treatment renders the articlessuitable for sealing with thin plastic films. Sealing articles with thinplastic films is a well-known process, and many suitable films are known(e.g., thin monolayer or multilayer sheets made of materials such aspolyethylene or polyvinylidene chloride, optionally including polymerlayers which inhibit passage of moisture or certain gases). Articles canbe sealed with plastic films, for example, by completely enveloping thearticle in the film and sealing the film to itself. Alternatively,articles can be sealed by sealing a film about the periphery of aconcavity, compartment, or other orifice defined by an article and, ifdesired, thereafter trimming the portion(s) of the film beyond thatperiphery. All technologies for sealing articles with thin plastic filmsare believed to involve at least intermittent contact between peripheralareas of the article and the film used for sealing.

It is therefore beneficial for an article to be sealed with a thinplastic film to be free, or at least substantially free, of sharp,pointed, rough, jagged, or abrasive structures, at least at areas of thearticle which contact the film. It is particularly important that suchstructures be absent from the surface of the article which willnecessarily contact sealing films, and highly desirable that thesestructures are also absent from article surfaces which are likely tocontact sealing films, whether during the sealing process, or whetherduring further packaging, shipping, unpackaging, or retail display ofthe film-sealed article. Still more preferably, articles to be wrappedwith a thin film bear no such structures at surfaces at which there is asubstantial likelihood of contact between the surface and the filmduring any of these processes. Ideally, the articles bear no suchsurface at any position at which a film used for sealing mightreasonably be expected to contact the surface position during theseprocesses.

A wide variety of thin plastic films are known to be useful for sealingcontainers, and substantially any of these films can be used to seal theshaped articles described herein (or compartments thereof). Selection ofsealing films (and materials for making shaped articles compatible withsuch sealing films) is well known in the art, and substantially anyknown combination of materials can be adapted for use with the shapedarticles described herein. By way of example, when a sealing film is tobe removably sealed about a shaped article described herein (e.g., anoverwrap film that is sealed to itself but not to the wrapped article),the materials used to make the shaped article should be selected suchthat it will not fuse with the film under the sealing conditions to beused. By contrast, when a sealing film is to be substantiallypermanently sealed to a shaped article (e.g., about the perimeter of acompartment defined by the article), the material(s) used to make thearticle should be selected to facilitate formation of a substantiallypermanent seal under practical processing conditions. Similarly,combinations of sealing and container materials and operating conditionsthat yield containers sealed with material that is peelable therefromare known and can be used.

One highly desirable embodiment of the articles described herein is atray-shaped article that is made by thermoforming (and that thereforepossesses potentially sharp peripheral edges prior to the edge-rollingtreatment described herein) such that it possesses about its entireperiphery the deflectable flange described herein and for which theperipheral edge is deflected beneath the extension and behind the spacerand bend region of the deflectable flange, about the entire periphery ofthe tray, sufficiently that the peripheral edge cannot be touched by ahuman fingertip that is swiped along the gap between the deflectedperipheral flange and the body of the tray, even if that fingertip isswiped along this gap around the entire periphery of the tray. Such atray will bear no sharp, pointed, rough, jagged, or abrasive edge at anyposition that can reasonably be expected to contacted by a sealing film,regardless of whether OW, VSP, or MAP technology is used in the sealingprocess. A tray suitable for use with all of these sealing technologiesis highly desirable and believed to be unavailable prior to thedisclosure of the subject matter described herein.

Many plastic films used for sealing of articles are flexible and do notthermoset over the range of temperatures ordinarily employed duringsealing and subsequent handling. Flexible films that are sealed tosurfaces are sometimes difficult to remove in a single piece from thesealing surface. For example, a flexible film that is sealed about theflat periphery of a tray may tear or split when one portion of the filmis pulled away from the tray, potentially requiring a user to remove thefilm in multiple passes or many strips or pieces. Such difficulties maybe particularly acute in situations in which the sealing surface isbroad, such as in a VSP-sealed package in which a sealing film may beadhered to or fused with a relatively large area of a tray on which anitem has been sealed between the film and the tray. The technologydescribed herein can be used to reduce or overcome this difficulty asfollows.

The shaped articles described herein (e.g., a tray-shaped article havinga smooth periphery) can be sealed with a thermosettable (i.e.,thermoformable) film to yield an article in which the thermoformablesealing film is heated above its glass transition temperature to softenit and applied against the smooth periphery of the shaped article. Athermoformable film that is heated above the glass transitiontemperature of the material of which it is made and thereafter cooledbelow that temperature will retain whatever conformation the film has(e.g., a conformation imposed upon it) when the temperature falls belowits glass transition temperature. Thus, if a thermoplastic film isformed “around” (i.e., extending more than about 90 degrees about) thesmooth outer periphery of an article described herein, the film will beheld to the article not only by whatever attraction or adhesion mayexist between the film and the article surface, but also by mechanicalforces (i.e., the film's resistance to deflection about the smooth outerperiphery), forming a structure analogous to a “snap off” lid.

Even though softened thin plastic films can be extremely delicate (e.g.,liable to be damaged by sharp, pointed, rough, jagged, or abrasivesurfaces), the smooth periphery of the shaped articles described hereinpermits even such delicate films to be applied thereto. In one example,a shaped article in the form of a tray having a smooth periphery can beVSP-sealed to encase an article between a softened thermoplastic sealingfilm and the tray, with little or no gas included within the sealedportion. Furthermore, the smooth periphery of the articles describedherein permits a softened film to be drawn, pressed, or formed aroundthe smooth periphery—that is, contacting not only the top portion of theperiphery (i.e., analogous to the extension 50 of the article edgedepicted in FIG. 9B), but around the bend region 150 of the deflectableflange, and along the spacer 140 and any bent or rounded portionsthereof (such as to or around the rounded underside 145 of the spacerdepicted in FIG. 9B) and thereafter set by reducing the temperature ofthe sealing film below its glass transition temperature. Such a sealwill form a relatively rigid “lid” and, even if the film is not adheredor fused to the shaped article where the film intersects the article,frictional forces or the shape of the “lid” (e.g., turned about therounded underside 145 of the spacer depicted in FIG. 9B, such that the“lid” must be stretched or expanded to disengage it from the rolled overperipheral flange 160) can hold the sealing film in place on thearticle. Furthermore, because softened thermosettable film can besubstantially thicker, therefore stronger, and/or more rigid than thinflexible sealing films, a thermosettable sealing film can form a seal or“lid” that can tend to be more likely removable in a single piece.

In one embodiment of the shaped articles described herein, for example,the article is a tray having a food item placed thereon, with athermosettable film draped across the food item and the periphery of thetray while the film is in a softened state; gas between the film and thetray is withdrawn to form a VSP-type seal (with the film closely opposedagainst the food item and the tray surface upon which the food itemrests); and the film is draped around (from the top, to or around, thebottom of the periphery), optionally sealed or fused to the tray,trimmed about the bottom of the tray periphery, and cooled. In thefinished tray, the “lid” formed upon cooling of the film must be“snapped off” the tray by stretching the edge of the lid around theperiphery of the tray, but once this operation is performed, the entirelid can be removed from the tray in a single piece.

In another embodiment, a shaped article described herein is sealed(after its smooth outer periphery has been formed) using athermoformable plastic film that is extended across a compartmentdefined by the article and at least about 90 degrees about opposedsmooth peripheral sides of the article (i.e., opposite ends of a roundedrectangular tray). The film is heated above its glass transitiontemperature and cooled below that temperature while extended about theopposed smooth peripheral sides. If desired, a vacuum or modifiedatmosphere can be applied to the compartment during such sealing. Theresulting article has a thermoset film cover that must be stretched (or“snapped”) around at least one peripheral side of the article in orderto remove the film from the article (in addition to any other seal thatmay exist between the film and the article).

The shaped article described herein can be used in ways which arebelieved to be not possible using previously-known trays. Typically,others have used containers especially designed and made for each of thevarious sealing technologies described herein (e.g., OW, VSP, and MAPtechnologies) for sealing containers with thin plastic films. That is,food trays designed for OW-sealing have been generally consideredunsuitable for VSP- and MAP-wrapping (e.g., owing to the lack ofsurfaces suitable for sealing in VSP- and/or MAP-technologies).Similarly, the sharp edges of many containers designed for use with VSP-and MAP-sealing technologies render those containers unsuitable foroverwrapping with fragile polymer films. The shaped articles describedherein can be used to make shaped articles that can suitably be used ascontainers for sealing by any of OW, VSP and MAP technologies. Becausethe shaped articles are thermoformed, container surfaces suitable forVSP- and/or MAP-sealing can be included in the shape of the articles.Using the methods described herein, any edges of a shaped article whichmight provide a risk of tearing sealing films (or, alternatively, alledges of the shaped article) can be made to have a smooth conformation,such as by forming a rolled-over edge or by smoothing the shape of themold used for thermoforming the precursor article. Thus, unlikepreviously-known trays, the shaped articles described herein can be usedwith substantially any film-sealing technology.

Other advantageous uses of the shaped articles described herein relateto the smoothness of their edges. The articles can be used insubstantially any environment in which it is desirable or necessary thata solid object exhibit smooth edges. By way of example, instruments usedin surgical procedures are typically packaged in openable containers (topermit reuse and sterilization between uses) that are opened bypersonnel wearing easily-torn surgical gloves during medical surgeryprocedures. Thermoformed articles (e.g., so-called “clam-shell” typesnap-open packages of known design) can be made as described herein,with those articles being initially made having a deflectable flangewherever they are cut from the web of thermoformed material, andthereafter rolling over that deflectable flange to yield the smooth edgedescribed herein. Articles made in this manner will present smooth edgesto users, reducing the likelihood that surgical gloves will be torn byopening such packages during surgery procedures. Similarly, thermoformedpackages of known design that are employed to facilitate handling, toinhibit theft, or to achieve other ends can be adapted (e.g., byincluding a deflectable flange in their design and rolling it over) totake advantage of the edge-smoothing technology described herein.

System for Forming Articles

As described above, precursors of the shaped articles described hereincan be formed by standard thermoforming methods, using standardthermoforming equipment. To do so, a thermoforming mold is used to makea precursor article by imposing upon a thermoplastic sheet the desiredconformation of the finished article, except that the deflectable flangedescribed herein is included at the peripheral edge(s) at which thesmooth periphery is to be formed. Upon cutting the precursor articlefrom the web of thermoplastic sheet, the edge-smoothing operationsdescribed herein can be performed by impinging the deflectable flangeupon the ram (optionally with the aid of an upper body).

Newly-thermoformed precursor articles will tend to emerge from thethermoformer at a temperature close to (but below) the glass transitiontemperature of the thermoplastic. Impinging the deflectable flange andthe ram shortly after removing the precursor article from thethermoformer can reduce the quantity of heat energy which must besupplied to one or more portions of the deflectable flange in order toachieve the desired deflection (or “rolled over” edge effect) of thedeflectable flange described herein. For this reason, it can bedesirable to combine the thermoformer, the ram, and an impingementmechanism into a single system or a single piece of equipment. Such asystem or piece of equipment should include i) a thermoformer modulecapable of forming the precursor article; ii) a cutter for cutting theprecursor article from a thermoplastic sheet or roll from which it wasformed; iii) the ram; and iv) a mechanism for positioning the precursorarticle against the ram (i.e., so that the deflectable flange portionsline up with the corresponding ram portions) and impinging the precursorarticle and the ram together. The heat required during the deflectableflange-deflection operations described herein can be provided by theram, by the cutter (e.g., using a heated cutting blade to heat theperipheral edge and an adjacent peripheral portion of the deflectableflange above the softening temperature of the thermoplastic), by aseparate heater (e.g., a radiant heating element disposed in closeopposition to the ram when it is engaged against the deflectableflange), or by a combination of these. The precise selection,orientation, order, and construction of these pieces of equipment arenot critical and can be selected by a skilled artisan in light of therequirements and processing steps described herein. The system orequipment can also include the plug described herein for insertionwithin a void in the precursor article prior to impingement of thedeflectable flange against the ram.

EXAMPLE

The subject matter of this disclosure is now described with reference tothe following Examples. These Examples are provided for the purpose ofillustration only, and the subject matter is not limited to theseExamples, but rather encompasses all variations which are evident as aresult of the teaching provided herein.

Example 1

FIGS. 6A and 6B illustrate a thermoplastic tray which was thermoformedfrom a flat sheet of thermoplastic material and then cut from the sheet.The sharp edge formed by the cutting process is shown in each of thesefigures, with a finger touching the sharp edge. After the smoothingprocess described herein was performed on these trays, the appearance ofthe trays was approximately that shown in FIG. 3, in which the sharpedge has been “rolled over” such that it faces the body of the tray anda smooth portion, formed by flexing at least the bend region of thedeflectable flange and heating and cooling it to yield a smooth outerperiphery to the tray which will not impact either upon a thin plasticfilm attached to the rim of the tray or upon a thin plastic film whichis snugly wrapped about the entirety of the tray.

Example 2

This example is provided for the sake of explaining formation andsealing of a shaped article as described herein. In this example,formation, filling, and sealing of a container containing a cut of freshfish is described.

A shaped article for receiving the fish is formed by traditionalthermoforming methods. A thermoformable material (e.g., PET) in sheetform is heated above its glass transition temperature and urged againsta mold using traditional thermoforming techniques (using either a maleor female mold, with or without the application of positive and/ornegative pressure to urge portions of the sheet against portions of themold). Such thermoforming yields a tray-shaped container having arounded rectangular shape overall and including a concave interiorportion for receiving the cut of fish. The rounded rectangular overallshape of the container is defined by a deflectable flange that surroundsthe interior portion about the entire perimeter of that interiorportion. The deflectable flange has the configuration shown in FIG. 1A,and the tray has the approximate shape of the tray shown in FIG. 6D uponcutting the thermoformed tray from the sheet at peripheral edge 110 ofthe deflectable flange 160. The die used to cut the tray from the sheetis heated so that the peripheral edge of the tray is at or near itsglass transition temperature.

A plug having a shape that substantially fills the interior portion ofthe tray at the portions adjacent the extension 50 of the deflectableflange 160 is inserted into the interior portion (approximately as shownin FIG. 8Dii). The plug-filled tray is then inserted into a ram 300(approximately as shown in the upper position in FIG. 10A, except thatno plug is present in FIG. 10A), so that the peripheral edge 110, thespacer 140, or both contact the upper surface 302 of the ram 300 atsubstantially all portions of the deflectable flange. Downward pressure(referring to FIG. 10A, the force being applied downwardly from the topof the image) is applied to the extension 50 of the deflectable flange160 about the entire periphery of the interior, driving the spacer 140and/or peripheral edge 110 portions of the deflectable flange 160against the ram. The deflectable flange is driven against the ram to aposition analogous to that shown in cross-section in FIG. 8H, and theparts are held in this position for a period of time sufficient for atleast the portion of the deflectable flange indicated by “B” in FIG. 8 Jto attain a temperature above its glass transition temperature by virtueof heat conducted or radiated thereto from the ram. The deflectableflange is thereafter urged (by the force applied to the extension 50)further against the ram so that the peripheral edge 110 slides, scrapes,or skips across the inner surface 302 of the ram 300 and the deflectableflange advances to approximately the position shown in FIG. 8J. Ifdesired, the deflectable flange can be further advanced to the positionshown in FIG. 8K, optionally upon pausing to permit additional portionsof the deflectable flange to achieve a temperature above its glasstransition point. Also, if desired, a coolant such as ambient air can beinjected (e.g. at the position occupied by element 120 in FIG. 8K) toreduce the temperature of the deflectable flange at the injection point,in order to prevent further irreversible deflection of such portion. Thedeflectable flange is urged against the ram sufficiently that theperipheral edge is not readily accessible to films or other materialspresent at the periphery of the tray.

The force urging the deflectable flange against the ram is discontinued,and the article is removed from contact with the ram, whereby thematerial of the deflectable flange cools below its glass transitiontemperature and retains its shape in the absence of applied force. Atthis point, a shaped article in the shape of the desired tray has beenformed, the tray having a smooth periphery. The tray can be usedimmediately for packaging the cut of fish or, more typically, it can bestacked with other such trays and shipped to a fish processor.

Whether the tray is used immediately after formation or retrieved byde-nesting the tray from a stack of trays, the cut of fish can now bedeposited within the interior compartment of the tray, together with anyother materials (e.g., sauce, an absorbent pad, vegetable, orseasonings) to be packaged therewith in preparation for sealing. Any ofa number of known sealing technologies can be used to seal the containerand the fish.

The tray can simply be over-wrapped with a thin plastic film (the filmextending across the opening of the compartment between extensions 50 onopposite sides of the compartment, around smoothly-bent bend region 150and/or spacer 140 of the deflectable flange 160), and the terminus ofthe film can be sealed to a portion of the film overlaying the tray, forexample by application of a heated pad against the terminus and theportion, followed by heat-shrinking of the film to yield a visuallypleasing taut film surface. Because the tray has no sharp or rough edgesat its periphery, the overwrapped film is not torn during sealing, nordo such edges tear, snag, or abrade other sealed packages duringshipping. The over-wrapped, fish-containing container can be packaged(e.g., in a box with other such containers or in a plastic bagcontaining both a selected gas or liquid phase and other suchcontainers), and shipped to a wholesaler, retailer, or customer.

Rather than sealing the package using an over-wrap that is sealed toitself, the container can be sealed after filling with a film that doesnot envelop the tray, but instead seals the compartment at the extension50 about the periphery of the compartment. Such a seal can be generatedby simply sealing a film (using any one or combination of heat,pressure, and an adhesive) to the extension 50 and, preferably, trimmingthe film about the periphery of the seal (e.g., by trimming the film atapproximately the peripheral extent of the container). If desired, anyfree ends of the film seal can be shrunk using heat. Prior to sealing, avacuum can be applied to withdraw gases from the interior of thecompartment and to draw the film against the contents of thecompartment, and a selected gas or gas mixture can optionally beinjected prior to sealing.

The disclosure of every patent, patent application, and publicationcited herein is hereby incorporated herein by reference in its entirety.

While this subject matter has been disclosed with reference to specificembodiments, it is apparent that other embodiments and variations can bedevised by others skilled in the art without departing from the truespirit and scope of the subject matter described herein. The appendedclaims include all such embodiments and equivalent variations.

What is claimed is:
 1. A tray amenable to sealing with a sealing filmusing each of overwrap (OW), vacuum-sealed packaging (VSP), and modifiedatmosphere packaging (MAP) sealing technologies, the tray being anarticle formed from a thermoplastic sheet having a peripheral edge, thearticle comprising a tray-shaped body having a concave portionsurrounded by an extension extending peripherally away from the concaveportion; the extension including the peripheral edge, a flat sealingsurface surrounding the concave portion, and a bent portion interposedbetween the peripheral edge and the sealing surface, the sealing surfacebeing suitable for sealing the sealing film thereto using either of VSPand MAP sealing technologies; and the article having a smooth peripheryand the bent portion being bent sufficiently that the peripheral edge isturned at least approximately opposite the periphery.
 2. The tray ofclaim 1, wherein a gap exists between the bent portion and the concaveportion of the body.
 3. The tray of claim 2, wherein the gap occursabout the entire periphery of the article.
 4. The tray of claim 3,wherein the width of the gap at each position about the concave body isat least half the width, measured in the direction extendingperipherally away from the concave portion of the body, of the sealingsurface at that position.
 5. The tray of claim 3, wherein the width ofthe gap at each position about the concave body being at leastthree-quarters the width, measured in the direction extendingperipherally away from the concave portion of the body, of the sealingsurface at that position.
 6. The tray of claim 1, wherein the bentportion has a conformation that is rolled in a direction opposite theperiphery of the tray.
 7. The tray of claim 6, wherein the bent portionis rolled beneath the underside of the extension and includes theperipheral edge, the bent portion and the peripheral edge defining arolled-over edge.
 8. The tray of claim 1, wherein the peripheral edge isturned away from the periphery of the tray.
 9. The tray of claim 1,having the overall shape of a rectangular tray with rounded corners. 10.The tray of claim 1, wherein the bent portion includes a roundedportion.
 11. The tray of claim 10, wherein the rounded portion has aJ-shaped conformation.
 12. The tray of claim 10, wherein the roundedportion has a U-shaped conformation.
 13. The tray of claim 10, whereinthe rounded portion has a spiral conformation.
 14. The tray of claim 1,wherein the sealing surface has a substantially constant width, measuredin the direction extending peripherally away from the concave portion ofthe body, about the entire concave portion.
 15. The tray of claim 1,having an geometric shape suitable for use in a tray-sealing apparatusin a MAP-sealing process.
 16. The tray of claim 1, the tray beingoverwrapped by the sealing film.
 17. The tray of claim 16, wherein theedge strength and rigidity of the tray are sufficient to resist thetendency of the overwrapped sealing film to cause the concave portion toclose upon itself.
 18. The tray of claim 1, the tray having the sealingfilm sealed to the sealing surface about the entire perimeter of theconcave portion.
 19. The tray of claim 18, wherein the edge strength andrigidity of the tray are sufficient to resist the tendency of thesealing film to cause the concave portion to close upon itself.
 20. Thetray of claim 18, wherein the sealing film extends peripherally from thesealing surface around the bent portion.
 21. The tray of claim 20,wherein the sealing film remains sealed to the sealing surfaceregardless of any attraction or adhesion may exist between the sealingfilm and the sealing surface.
 22. The tray of claim 18, wherein thesealing film is thermosettable, is extends at least about 90 degreesabout the smooth periphery of the article, and is below its glasstransition temperature.
 23. The tray of claim 1, wherein the concaveportion of the tray is visually clear.
 24. The tray of claim 23, whereinthe bent portion of the tray is visually clear.
 25. The tray of claim 1,wherein the extension includes a bend region interposed between thesealing surface and the peripheral edge and a spacer interposed betweenthe bend region and the peripheral edge, the bend region having a smoothcontour and interconnecting the spacer with the portion of the extensionbearing the sealing surface, and the bent portion at least partiallyencompassing at least one of the spacer and the bend region.
 26. Thetray of claim 25, wherein the spacer includes a flat portion and bearsthe bent portion at the end of the spacer bearing the peripheral edgeand wherein the bend region interconnects the flat portion of the spacerat an approximately right angle with the portion of the extensionbearing the sealing surface.
 27. The tray of claim 26, wherein theheight of the flat portion of the spacer, measured from the bend regionto the nearest part of the bent portion, is substantially constantaround the entire periphery of the tray.
 28. The tray of claim 26,wherein the height of the flat portion of the spacer, measured from thebend region to the nearest part of the bent portion, is substantiallyconstant around the entire periphery of the tray, other than at one ormore stacking extensions at which the height of the flat portion of thespacer is greater.
 29. The tray of claim 28, having the conformation ofa rectangular tray with rounded corners and bearing a stacking extensionat each of the rounded corners.
 30. A tray amenable to sealing with asealing film using each of overwrap (OW), vacuum-sealed packaging (VSP),and modified atmosphere packaging (MAP) sealing technologies, the traybeing an article formed from a thermoplastic sheet having a peripheraledge, the article comprising a tray-shaped body having a concave portionsurrounded by an extension extending peripherally away from the concaveportion; the extension including the peripheral edge, a flat sealingsurface surrounding the concave portion, and a bent portion interposedbetween the peripheral edge and the sealing surface, the sealing surfacebeing suitable for sealing the sealing film thereto using either of VSPand MAP sealing technologies; and the article having a smooth peripheryand the bent portion being bent sufficiently that the peripheral edge ofthe thermoplastic sheet is rendered substantially incapable ofcontacting the sealing film of a second such tray that has been sealedwith the sealing film using the same sealing technology when theperiphery of the tray is contacted with the sealing film of the secondtray.